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Letrozole is an anticancer medication prescribed for the management of estrogen receptor-positive breast cancer in postmenopausal women. Chronic pain is prevalent in patients receiving chemotherapy, leading to the use of adjuvant analgesics such as tramadol. This work introduces the first analytical approach for the concurrent quantification of letrozole and tramadol, two co-administered drugs, employing a rapid, highly sensitive, eco-friendly, and cost-effective first derivative synchronous spectrofluorimetric technique. The fluorescence of tramadol and letrozole was measured at wavelengths of 235.9 nm and 241.9 nm, respectively using a wavelength difference (Δλ) of 60.0 nm. The developed approach demonstrated exceptional linearity (r ˃ 0.999) within the specified concentration ranges for tramadol (10.0-1200.0 ng/mL) and letrozole (1.0-140.0 ng/mL). The results demonstrated that the proposed technique exhibits a high level of sensitivity, with detection limits of 0.569 and 0.143 ng/mL for tramadol and letrozole, respectively, indicating the good bioanalytical applicability. The within-run precisions, both intra-day and inter-day, for both analytes, were less than 0.71 % RSD. The developed approach was effectively applied to simultaneously estimate the mentioned drugs in their tablets and human plasma samples, achieving high percentage recoveries and low % RSD values. In order to assess the environmental sustainability of the developed approach, Analytical GREEnnessNNESS (AGREE) and the Green Analytical Procedure Index (GAPI) metric tools were employed. Both tools revealed that the developed approach is excellent green, suggesting its usage as an environmentally-friendly alternative for the routine assayof the investigated pharmaceuticals. The developed approach was validated according to the ICHQ2 (R1) requirements., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In the current study, nickel oxide nanoparticles (NiO NPs) modified with dimethylglyoxime (DMG) were deposited onto the cellulose surface (Ni(DMG) 2 -NiO-Cell) and used as an efficient adsorbent for thin film microextraction (TFME) of tramadol (TRA). The extracted TRA was determined using a high-performance liquid chromatography-ultraviolet detector (HPLC-UV). NiO NPs were synthesized by co-precipitation method on the surface of the cellulose substrate; afterward, its surface was modified by DMG to increase the extraction capability of the thin film toward TRA. The synthesized NiO-Cell and Ni(DMG) 2 -NiO-Cell thin films were characterized using various techniques. The effect of modification of the NiO thin film with DMG reagent on the extraction efficiency was investigated. The crucial parameters influencing the extraction efficiency, including extraction time, desorption time, desorption solvent, pH and salt content, were investigated via a one-at-a-time approach. The figures of merit for the developed method were evaluated in urine, plasma, and deionized water under the optimized extraction and desorption condition. The limits of detection and limits of quantification were in the range of 0.1 to 1 ng mL -1 and 0.3 to 3 ng mL -1 , respectively, for the studied samples. The linear dynamic ranges of the developed TFME-HPLC-UV method were 0.3-1000, 1-2500, and 3-5000 ng mL -1 for the deionized water, urine, and plasma samples, respectively. The reproducibility and repeatability of the developed method was assayed in terms of intra-day, inter-day, and inter-thin film precisions by conducting six-replicate experiments at the concentration level of 0.1 and 1 μg mL -1 , which were in the range of 5.9% to 8.3%. The sufficiency and applicability of the developed TFME-HPLC-UV method was investigated by determining TRA in urine and plasma samples, and the resulting relative recoveries (RR%) were 85.9% and 91.7%, respectively.

Ultrasonic-assisted dispersive micro solid phase extraction (UA-DMSPE) is proposed as a fast and easy technique for the extraction and preconcentration of methadone and tramadol from serum samples. Different sorbents including carbon nanotubes, oxidized carbon nanotubes, and TiO 2 nanoparticles were compared to extract methadone and tramadol. The best performance was obtained using oxidized carbon nanotubes due to the strong affinity between the drugs and carbon nanotube adsorbents. Final analysis of drugs performed by using gas chromatography-mass spectrometric detection. Different parameters affecting the extraction efficiency, such as the sample volume, amount of adsorbent, desorption solvent type and volume, centrifugation time, and speed were investigated and optimized. The striking features of this technique are correlated to its speed and the small volumes of sample (about 1 mL), desorption solvent (about 50 μL), and adsorbent (about 0.001 g) for analysis of drugs, and finally, milder centrifugation conditions relative to the previously reported adsorbent. The optimal parameters were achieved as follows: pH value was set at 9, the sample volume was adjusted to 1200 µL, the amount of adsorbent used was 1 mg, the extraction time was set at 5 min, and the volume of the desorption solvent was adjusted to 50 µL. The limits of detections (0.5 and 0.8 ng mL -1 ) and quantifications (1.5 and 2.5 ng mL -1 ) were obtained for methadone and tramadol, respectively. The developed method also showed good repeatability, relative standard deviation (RSD) of 9.49 % and 7.47 % (n = 5), for the spiked aqueous solution at the concentration level of 10, 50, and 100 ng mL -1 for analytes, and linearity, R ≥ 0.9809. The results showed that UA-DMSPE is a quick, relatively inexpensive, and environmentally friendly alternative technique for the extraction of opiate drugs from serum samples., Competing Interests: Declaration of competing interest All authors declare that they have no conflict of interest., (Copyright © 2024. Published by Elsevier B.V.)

One of the most common features of many different clinical conditions is pain; hence, there is a crucial need for eliminating or reducing it to a tolerable level to retrieve physical, psychological and social functioning. A first derivative synchronous spectrofluorimetry technique is proposed for the simultaneous determination of celecoxib and tramadol HCl, a recent coformulation authorized for treating acute pain in adults. The method includes using synchronous spectrofluorimetry at ∆λ = 80 nm where tramadol HCl was determined using first derivative technique at λ = 230.2 nm, while celecoxib was determined at λ = 288.24 nm. The proposed method was successfully applied to their co-formulated dosage forms in addition to spiked human plasma and validated in agreement with the guidelines of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH). The linear ranges were found to be 0.50-5.0 and 0.15-0.50, the limits of detection to be 0.088 and 0.011 and the limits of quantification to be 0.266 and 0.032 μg/ml for celecoxib and tramadol, respectively. Statistical analysis revealed no significant difference when compared with previously reported methods as evidenced by the values of the variance ratio F-test and Student t-test. The proposed method was successfully applied to commercial dosage forms and spiked human samples. Moreover, the greenness of the proposed method was investigated based on the analytical eco-scale approach, with the results showing an excellent green scale with a score of 95., (© 2024 John Wiley & Sons Ltd.)

Multimodal analgesia is employed in paediatric pain management to maximise analgesia and minimise side effects. Tramadol is dosed at 1-1.5 mg/kg to treat severe pain in children but the assay for tramadol in plasma samples for pharmacokinetic and toxicology studies does not often consider concurrently administered medications. In this study we developed and validated an HPLC-UV method to quantify tramadol and its main metabolite (O-desmethyltramadol) in human plasma in the presence of seven potentially interfering drugs. Sample preparation method was developed by combining liquid-liquid extraction and protein precipitation. Chromatographic separation was achieved on a BDS-Hypersil-C18 column (5 µm, 250 × 4.6 mm) using a double gradient method. The limit of quantification was 6.7 ng/ml for both tramadol and ODT. The precision and accuracy were in compliance with ICH guidelines. This method was successfully employed to analyse the blood samples of 137 paediatric participants in a tramadol pharmacokinetic trial., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The introduced research presents a novel in vivo quantitative method for assay of mixtures of pregabalin and tramadol as a common combinations approved for treatment of neuropathic pain. Green analytical chemistry is a recently emerging science concerned with control of the use of chemicals harmful to the environment in various analytical methods. Consequently, a green high-performance thin layer chromatography (HPTLC) method was achieved for determination of the mixture in human plasma and urine satisfying both analytical and environmental standards. The separation was achieved on HPTLC sheets using a separating mixture of ethanol-ethyl acetate-acetone-ammonia solution (8:2:1:0.05, by volume) as a mobile phase. The sheets were dried in air then scanned at two wavelengths. For tramadol, 220 nm was chosen; however, pregabalin is an unconjugated drug, so its determination was a challenge. Hence for pregabalin, the plates were sprayed with ethanolic solution of ninhydrin (3%, w/v), to obtain a conjugated complex, which could be assessed at 550 nm. Furthermore, the developed method fulfilled the US Food and Drug Administration validation guidelines, and proved to be useful in therapeutic drug monitoring of this combination. The Eco-scale assessment protocol was implemented to determine the greenness profile of the applied method., (© 2020 John Wiley & Sons Ltd.)

Tramadol is used as an analgesic in humans and some animal species. When tramadol is administered to most species it undergoes metabolism to its main metabolites M1 or O-desmethyltramadol, and M2 or N-desmethyltramadol, and many other metabolites. This study describes the pharmacokinetic profile of tramadol when a single subcutaneous bolus of 2 mg/kg was initially administered to two koalas. Based on the results of these two koalas, subsequently 4 mg/kg as a single subcutaneous injection, was administered to an additional four koalas. M1 is recognised as an active metabolite and has greater analgesic activity than tramadol, while M2 is considered inactive. A liquid chromatography assay to quantify tramadol, M1 and M2 in koala plasma was developed and validated. Liquid chromatography-mass spectrometry confirmed that M1 had been identified. Additionally, the metabolite didesmethyltramadol was identified in chromatograms of two of the male koalas. When 4 mg/kg tramadol was administered, the median half-life of tramadol and M1 were 2.89 h and 24.69 h, respectively. The M1 plasma concentration remained well above the minimally effective M1 plasma concentration in humans (approximately 36 ng/mL) over 12 hours. The M1 plasma concentration, when tramadol was administered at 2 mg/kg, did not exceed 36 ng/mL at any time-point. When tramadol was administered at 2 mg/kg and 4 mg/kg the area under the curve M1: tramadol ratios were 0.33 and 0.50, respectively. Tramadol and M1 binding to plasma protein were determined using thawed, frozen koala plasma and the mean binding was 20% and 75%, respectively. It is concluded that when tramadol is administered at 4 mg/kg as a subcutaneous injection to the koala, it is predicted to have some analgesic activity., Competing Interests: The authors have declared that no competing interests exist.

This study aimed to evaluate the influence of CYP2D6 activity and cachexia progression on the enantiomeric alteration of plasma tramadol and its demethylated metabolites in head and neck cancer patients. Fifty-three head and neck cancer patients receiving oral tramadol were enrolled. The plasma concentrations of tramadol, O-desmethyltramadol (ODT) and N-desmethyltramadol (NDT) enantiomers were determined. The CYP2D6 activity score (AS) and degree of cachexia progression were assessed according to genotype and the Glasgow Prognostic Score (GPS), respectively. The enantiomeric ratio of NDT was (+)-form dominant in all patients. CYP2D6 AS had negative correlations with the plasma concentrations of (+)-NDT and (-)-NDT. The plasma concentrations of (+)-tramadol and (+)-ODT were higher in patients with GPS 1 or 2 than in those with GPS 0. Lower metabolic ratios to NDT enantiomers were observed in patients with GPS 1 or 2. In patients with GPS 1 or 2, the plasma (-)-tramadol was associated with the incidence of central nervous system symptoms. In conclusion, CYP2D6 AS partially explained the contribution of CYP2D6 activity to plasma tramadol and its demethylated metabolite enantiomers. Additionally, cachexia progression elevated the plasma (+)-tramadol and (+)-ODT levels through the reduction of N-demethylation of (+)-tramadol., (© 2020 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).)

The analgesics, codeine, fentanyl, oxycodone and tramadol, frequently occur in postmortem cases and determining their role in the cause of death can be challenging. However, postmortem blood is susceptible to redistribution and may not be available in cases of severe blood loss, putrefaction or burns. Brain tissue may serve as a viable supplement to blood or on its own, as it is resistant to postmortem redistribution and often available as a sample matrix when blood is not available. We present brain and blood concentrations and brain-blood ratios of the four analgesics from 210 autopsy cases. The cases were classified according to the presumed cause of death: A: The compound was believed to have solely caused a fatal intoxication. B: The compound was assumed to have contributed to a fatal outcome in combination with other drugs, alcohol or disease. C: The compound was not regarded as being related to the cause of death. Blood and brain samples were prepared by automatic solid phase extraction and quantified by liquid chromatography-mass spectrometry. The squared correlation coefficients between concentrations in brain tissue and blood ranged 0.45-0.91. The median brain-blood ratios were codeine 1.8 (range 0.47-4.6), fentanyl 2.1 (range 0.29-16), oxycodone 1.8 (range 0.11-6.0) and tramadol 1.8 (range 0.047-6.8). A significantly higher brain-blood ratio of codeine was observed in cases where heroin had been administered, although there was a wide overlap. Intravenous and transdermal fentanyl administration could not be distinguished based on the blood or brain concentration or the brain-blood ratio. The results of this study may benefit the toxicological investigation in postmortem cases where one of the four analgesics are suspected of having contributed to or caused a fatal intoxication., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Tramadol is a weak opioid that produces analgesic effect via both the μ-opioid receptor (MOR) and non-opioid targets. Constipation is the most common opioid-related side effect in patients with cancer and non-cancer pain. However, the contribution of MOR to tramadol-induced constipation is unclear. Therefore, we used naldemedine, a peripherally acting MOR antagonist, and MOR-knockout mice to investigate the involvement of peripheral MOR in tramadol-induced constipation using a small intestinal transit model. A single dose of tramadol (3-100 mg/kg, per os (p.o.)) inhibited small intestinal transit dose-dependently in rats. Naldemedine (0.01-10 mg/kg, p.o.) blocked the inhibition of small intestinal transit induced by tramadol (30 mg/kg, p.o.) in rats. The transition rate increased dose-dependently over the range of naldemedine 0.01-0.3 mg/kg, and complete recovery was observed at 0.3-10 m/kg. Additionally, tramadol (30 and 100 mg/kg, subcutaneously (s.c.)) inhibited small intestinal transit in wild-type mice but not in MOR-knockout mice. These results suggest that peripheral MOR participates in tramadol-induced constipation.

Tramadol is a synthetic opioid drug used in the treatment of chronic and acute pain. An abnormal prevalence of its misuse in elite sport to overcome pain resulting from prolonged physical effort was recently reported. However, besides its antinociceptive effects, tramadol consumption is associated with negative effects such as numbness, confusion, and reduced alertness. This fact prompted the Union Cycliste Internationale to ban the use of tramadol in cycling competitions. Herein, we present the development of a dried blood spot (DBS) sample collection and preparation method followed by a liquid-chromatography mass spectrometry (LC-MS) analysis to rapidly determine the presence of tramadol and its two main metabolites in blood samples. The detection window of each analyte was evaluated and the analysis of performance on various MS platforms (HRMS and MS/MS) was assessed. Tramadol and its two main metabolites were detected up to 12 h after the intake of a single dose of 50 mg of tramadol in positive controls. In professional cycling competitions, 711 DBS samples collected from 361 different riders were analysed using the developed methodology, but all returned negative results (absence of parent and both metabolite compounds). In the context of professional cycling, we illustrate a valid method bringing together the easiness of collection and minimal sample preparation required by DBS, yet affording the performance standards of MS determination. The proposed method to detect tramadol and its metabolites was successfully implemented in cycling races with a probable strong deterrent effect., (© 2020 John Wiley & Sons, Ltd.)

A magnetic nanocomposite adsorbent based on Zn-Al layered double hydroxide (LDH) intercalated with tyrosine has been synthesized for ultrasound-assisted extraction of two drugs of abuse: tramadol (TRA) and methadone (MET). Analysis was carried out using gas chromatography-mass spectrometry. The synthesized LDH was characterized by Fourier transform-infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The most important extraction parameters such as type of the elution solvent, pH value of the sample solution, and the amount of the adsorbent were optimized. With assistance of ultrasound radiation, the maximum extraction of target drugs using the fabricated LDH was achieved within 5 min. Under the optimized conditions, the limits of determination were 0.45, 0.45, 2.5, and 0.8 μg L -1 for TRA and 0.15, 0.15, 1.2, and 0.5 μg L -1 for MET in water, urine, plasma, and saliva samples, respectively. The preconcentration factors obtained were in the range of 50-145. The matrix effect for MET and TRA is considerable in plasma (66%, 18%) and saliva (72%, 34%), respectively. The precision was found to be better 11% RSD. The maximum adsorption capacity is 4.84 (mg g -1 ) (L mg -1 ) 1/n based on the Freundlich isotherm. The proposed method presents good results for trace determination of tramadol and methadone in biological samples with satisfactory repeatability. Graphical abstract.

Phase I tramadol metabolism requires cytochrome p450 family 2, subfamily D, polypeptide 6 (CYP2D6) to form O-desmethyltramadol (M1). CYP2D6 genetic variants may infer metabolizer phenotype; however, drug ADME (absorption, distribution, metabolism, and excretion) and response depend on protein pathway(s), not CYP2D6 alone. There is a paucity of data regarding the contribution of trans-acting proteins to idiosyncratic phenotypes following drug exposure. A genome-wide association study identified five markers (rs79983226/kgp11274252, rs9384825, rs62435418/kgp10370907, rs72732317/kgp3743668, and rs184199168/exm1592932) associated with the conversion of tramadol to M1 (M1:T). These SNPs reside within five genes previously implicated with adverse reactions. Analysis of accompanying toxicological meta-data revealed a significant positive linear relationship between M1:T and degree of sample polypharmacy. Taken together, these data identify candidate loci for potential clinical inferences of phenotype following exposure to tramadol and highlight sample polypharmacy as a possible diagnostic covariate in post-mortem genetic studies.

An electrochemical sensing platform based upon screen-printing electrodes (SPEs) modified with nanostructured lanthanide metal oxides facilitate the detection of the widely misused drugs acetaminophen (ACP) and tramadol (TRA). Among the metal oxides examined, Yb 2 O 3 nanoplates (NPs) were found to give rise to an optimal electrochemical response. The electroanalysis of ACP and TRA individually, and within mixtures, was performed using cyclic and differential pulse voltammetry. The ACP and TRA exhibited non-overlapping voltammetric signals at voltages of +0.30 and + 0.67 V (vs. Ag/AgCl; pH 9) using Yb 2 O 3 -SPEs. Pharmaceutical dosage forms and spiked human fluids were analyzed in wide linear concentration ranges of 0.25-654 and 0.50-115 μmol.L -1 with limits of detection (LOD) of 55 and 87 nmol.L -1 for ACP and TRA, respectively. The Yb 2 O 3 -SPEs offer a sensitive and chemically stable enzyme-free electrochemical platform for ACP and TRA assay. Graphical abstractSchematic presentation of one-shot electrochemical analysis of misused drugs, tramadol (TRA) and acetaminophen (ACP) by utilizing ytterbium oxide nanoplates modified screen-printed electrodes (Yb 2 O 3 -SPEs). The Yb 2 O 3 -SPEs showed interesting responses for ACP and TRA within pharmaceutical formulations and human fluids.

The widespread use of opioids for the treatment of moderate or severe acute and chronic pain has become a public health problem due to the physical and psychological dependence and tolerance they produce. The increasingly higher doses that patients require may reach toxic levels or lead to accidents, including fatalities. We present the case of a welder who, while working for a shipping container company, fell from height without a safety harness and subsequently died as a result of a traumatic brain injury. Post-mortem examination revealed a cardiac blood tramadol concentration of 2.83 mg/L, which is 3-4 times higher than the maximum therapeutic dose. The combined use of synthetic opioids and antidepressants may heighten the adverse neurological and psychiatric effects. A review of the literature, identified studies, including previous reports of fatalities, supported our causal hypothesis of a serotonin syndrome. This syndrome can lead to a loss of cognitive and sensory capacity, interfere with decision-making ability, and produce mental confusion and dizziness, among other symptoms. In order to prevent harm to themselves and others, all persons who are currently taking these kinds of drugs should avoid dangerous tasks at work and must be advised by a physician regarding the type of activities that are safe for them to perform.

A sensitive method for quantitation of JW5473 in rat plasma has been established using ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI/MS/MS). Tramadol was used as an internal standard. JW5473 and internal standard in plasma sample was extracted using acetonitrile (protein precipitation). A centrifuged upper layer was then evaporated and reconstituted with the mobile phase of 0.5% formic acid-acetonitrile (40:60, v/v). The reconstituted samples were injected into a C 18 reversed-phase column. Using MS/MS in the multiple reaction monitoring (MRM) mode, JW5473 and tramadol were detected without severe interference from rat plasma matrix. JW5473 produced a protonated precursor ion ([M+H] + ) at m/z 432.3 and a corresponding product ion at m/z 114.4. And the internal standard produced a protonated precursor ion ([M+H] + ) at m/z 264.4 and a corresponding product ion at m/z 58.1. Detection of JW5473 in human plasma by the UPLC-ESI/MS/MS method was accurate and precise with a quantitation limit of 1.0 ng/mL. The validation, reproducibility, stability, and recovery of the method were evaluated. The method has been successfully applied to pharmacokinetic studies of JW5473 in rat plasma. Pharmacokinetic parameters of JW5473 was evaluated after intravenous (i. v.; at doses of 15 mg/kg) and oral (p.o.; at doses of 30 mg/kg) administration of JW5473 in rats. After p.o. administration (30 mg/kg) of JW5473, F (Fraction absorbed) value was approximately 70.5%., Competing Interests: There was no conflict of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: Age-related changes in the concentration-effect relationship of (+)-O-desmethyl-tramadol [(+)-ODM], tramadol's active metabolite, are not documented in the elderly., Objective: The objective of this study was to characterize, in elderly and young subjects, the (+)-ODM pharmacokinetic and pharmacodynamic relationship to examine the effect of age after single-dose administration of tramadol 200 mg extended-release tablets., Methods: A population analysis of a double-blind, randomized, placebo-controlled, two-period cross-over study including 13 elderly (aged ≥75 years) subjects with mild renal insufficiency and 16 young (aged 18-40 years) subjects was conducted. For 48 h post-dose, blood samples were collected and pain tolerance thresholds measured using an electrically stimulated pain model. A pharmacokinetic/pharmacodynamic model incorporating a one-compartment pharmacokinetic model for (+)-ODM parameterized with first-order formation rate, clearance (CL/f m ), volume of distribution (V/f m ) and a sigmoid maximum effect (E max ) model incorporating baseline (E 0 ) and placebo effect was used., Results: Maximum plasma concentrations of (+)-ODM occurred later and plasma concentrations declined more slowly in the elderly than in young subjects. In the elderly, V/f m was 76% larger and CL/f m 16% slower. Baseline (E 0 ) and sensitivity (C 50 ) for pain tolerance were similar between young and elderly subjects. However, the E max parameter was 2.5 times higher in the elderly and maximum possible treatment-related effect was 169 (135-221) in the young and 194 (149-252) in the elderly; that is, 15% higher in the elderly., Conclusions: This exploratory analysis suggests that age-related differences exist in the distribution and elimination of (+)-ODM, including a 76% larger distribution outside the central compartment and 16% slower clearance of (+)-ODM. These pharmacokinetic changes are associated with a 15% higher maximum possible treatment-related effect and carry the potential for greater efficacy but also the potential for increased side effects at the same dose in elderly subjects. Clinicaltrials.gov identifier: NCT02329561.

This study documents the pharmacokinetics of oral tramadol in Muscovy ducks. Six ducks received a single 30 mg/kg dose of tramadol, orally by stomach tube, with blood collection prior to and up to 24 hr after tramadol administration. Plasma tramadol, and metabolites O-desmethyltramadol (M1), and N,O-didesmethyltramadol (M5) concentrations were determined by high-pressure liquid chromatography (HPLC) with fluorescence (FL) detection. Pharmacokinetic parameters were calculated using a one-compartment model with first-order input. No adverse effects were noted after oral administration. All ducks achieved plasma concentrations of tramadol above 0.10 μg/ml and maintained those concentrations for at least 12 hr. Elimination half-life was 3.95 hr for tramadol in ducks, which is similar to other avian species. All ducks in this study produced the M1 metabolite and maintained plasma concentrations above 0.1 μg/ml for at least 24 hr., (© 2018 John Wiley & Sons Ltd.)

Objective: Chronic pancreatitis (CP) is a disease leading to irreversible pancreas dysfunction. One of the main symptoms is pain. Many patients require pharmacological therapy which should be started with paracetamol or, in selected groups of patients, ketoprofen. If the effect of ketoprofen is irrelevant, patients receive tramadol. The aim of this study is the evaluation of ketoprofen and tramadol pharmacokinetics (PK) in CP patients., Patients and Methods: 36 patients were divided into two groups: I - receiving ketoprofen (n=18; mean [SD] age, 48.61 [13.32] years; weight, 73.28 [20.48] kg), II - receiving tramadol (n=18; mean [SD] age, 46.78 [10.28] years; weight, 74.22 [14.04] kg, and BMI (Body Mass Index), 24.61 [4.51] kg/m2). The plasma concentrations of ketoprofen and tramadol with its active metabolite M1 (0-desmethyltramadol) were measured with the validated high-performance liquid chromatography method., Results: The main PK parameters for ketoprofen were as follows: Cmax (maximum plasma concentration), 3.41 [2.32] mg/L; AUC0-inf (area under the plasma concentration-time curve from time zero to infinity), 10.45 [5.57] mg⋅h/L; tmax (time to first occurrence of Cmax), 1.94 [1.25] h; Cl (clearance), 0.199 [0.165] L/kg·h, and Vd/kg (volume of distribution per kilogram of body weight), 0.71 [0.58] L/kg. The main PK parameters for TRM and M1 were as follows: Cmax, 226.4 [80.5] and 55.6 [23] ng/mL; AUC0-inf, 1903.3 [874.8] and 790.4 [512.4] ng⋅h/mL; tmax, 1.78 [0.73] and 2.67 [1.19] h, respectively., Conclusions: Chronic pancreatitis led to a decrease in the total amount of absorbed ketoprofen. Consequently, the analgesic effect of the drug may be weaker. Cmax of tramadol for most CP patients was within the therapeutic range associated with its analgesic activity. M1/TRM ratios for Cmax and AUC were unchanged.

We evaluated the effects of therapeutic and supratherapeutic doses of tramadol hydrochloride on the corrected QT (QTc) interval in healthy adults (aged 18-55 years) in a randomized, phase I, double-blind, placebo- and positive-controlled, multiple-dose, 4-way crossover study. Participants were randomized to receive 1 of 4 treatments (A-D), 1 each in 4 treatment periods (1-4), separated by a washout period (7-15 days). Treatment A comprised tramadol 400 mg (therapeutic dose) on days 1 through 3, tramadol 100 mg and moxifloxacin-matched placebo on day 4, and placebo on all 4 days. Treatment B comprised tramadol 600 mg (supratherapeutic dose) on days 1 through 3, and tramadol 150 mg and moxifloxacin-matched placebo on day 4. Treatment C comprised placebo on days 1 through 4 and moxifloxacin-matched placebo on day 4. Treatment D comprised placebo on days 1 through 4 and moxifloxacin 400 mg on day 4. Of 68 participants enrolled, 57 (83.8%) completed the study. Both therapeutic and supratherapeutic doses of tramadol were shown to be noninferior to placebo regarding their effect on QTc prolongation. Sixty-one of 68 (89.7%) participants reported at least 1 treatment-emergent adverse event (mild); nausea was the most frequently reported treatment-emergent adverse event. Summarizing, tramadol at doses up to 600 mg/day did not cause clinically relevant QTc interval prolongation in healthy adults., (© 2018 The Authors. Clinical Pharmacology in Drug Development Published by Wiley Periodicals, Inc. on behalf of The American College of Clinical Pharmacology.)

Tramadol is used frequently in the management of mild to moderate pain conditions in dogs. This use is controversial because multiple reports in treated dogs demonstrate very low plasma concentrations of O -desmethyltramadol (M1), the active metabolite. The objective of this study was to identify a drug that could be coadministered with tramadol to increase plasma M1 concentrations, thereby enhancing analgesic efficacy. In vitro studies were initially conducted to identify a compound that inhibited tramadol metabolism to N -desmethyltramadol (M2) and M1 metabolism to N , O -didesmethyltramadol (M5) without reducing tramadol metabolism to M1. A randomized crossover drug-drug interaction study was then conducted by administering this inhibitor or placebo with tramadol to 12 dogs. Blood and urine samples were collected to measure tramadol, tramadol metabolites, and inhibitor concentrations. After screening 86 compounds, fluconazole was the only drug found to inhibit M2 and M5 formation potently without reducing M1 formation. Four hours after tramadol administration to fluconazole-treated dogs, there were marked statistically significant ( P < 0.001; Wilcoxon signed-rank test) increases in plasma tramadol (31-fold higher) and M1 (39-fold higher) concentrations when compared with placebo-treated dogs. Conversely, plasma M2 and M5 concentrations were significantly lower (11-fold and 3-fold, respectively; P < 0.01) in fluconazole-treated dogs. Metabolite concentrations in urine followed a similar pattern. This is the first study to demonstrate a potentially beneficial drug-drug interaction in dogs through enhancing plasma tramadol and M1 concentrations. Future studies are needed to determine whether adding fluconazole can enhance the analgesic efficacy of tramadol in healthy dogs and clinical patients experiencing pain., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

Using forensic autopsy-based data from a regional medical examiner office in the midwestern U.S. with a mixed small urban-rural population, we describe the characteristics of all-terrain vehicle (ATV)-related deaths occurring between 2000 and 2018. During this period, there were 25 ATV-related deaths. There was a strong male predominance with 22 male and 3 female decedents. The average age at death was 35 years, with a range from 10 to 82 years, and a bimodal age distribution with one peak at 10-19 years old, and a second peak at 60-69 years old. The most common cause of death was blunt trauma (n = 22), with the remainder being torso compression (n = 1), drowning (n = 1) and hypothermia (n = 1). Of the 22 blunt trauma deaths, 15 were due to head trauma. The most common mechanism of accident was roll-over (n = 11), followed by striking a stationary object (n = 6). Of the stationary objects struck, the most common was cable wire fencing accounting for 3 of the 6. A survival period following discovery of the body was present in 11 of the 25 deaths. Postmortem toxicology was positive for ethanol in 7 deaths and tramadol in 1 death.

The stereoselective analysis and separation of racemic drugs play an important role in pharmaceutical industry to eliminate the unwanted isomer and find the right therapeutic control for the patient. Present study suggests a maltodextrin-modified capillary electrophoresis method for a single-run chiral separation of two closely similar opiate pain relief drugs: tramadol (TRA) and methadone (MET). The best separation method possible for the both enantiomers was achieved on an uncoated fused-silica capillary at 25°C using 100 mM phosphate buffer (pH 8.0) containing 20% (w v -1 ) maltodextrin with dextrose equivalent of 4-7 and an applied voltage of 16 kV. Under optimal conditions, the baseline resolution of TRA and MET enantiomers was obtained in less than 12 minutes. The relative standard deviations (n = 3) of 20 μg mL -1 TRA and MET were 2.28% and 3.77%, respectively. The detection limits were found to be 2 μg mL -1 for TRA and 1.5 μg mL -1 for MET. This method was successfully applied to the measurement of drugs concentration in their tablets, urine, and plasma samples., (© 2018 Wiley Periodicals, Inc.)

Background: The impact of tramadol in children given acetaminophen-ibuprofen combination therapy is uncertain in acute pediatric pain management. A model describing the interaction between these three drugs would be useful to understand the role of supplemental analgesic therapy., Methods: Children undergoing tonsillectomy were given oral paracetamol and ibuprofen perioperatively. Blood was taken for paracetamol and ibuprofen drug assay on up to six occasions over 6 h after the initial dose. Tramadol was administered by caregivers for unacceptable postoperative pain. Pain was measured using the Parent's Postoperative Pain Measurement rating two hourly on the first postoperative day. A first-order absorption, one-compartment linear model with first-order elimination was used to describe acetaminophen and ibuprofen disposition. Analgesia was described using an E MAX model extended for three drugs, assuming additive effects. Curve fitting was performed using nonlinear mixed effects models., Results: Pharmacodynamic parameter estimates, expressed using fractional Hill equation, were maximum effect (E MAX ) 0.65 (95%CI 0.54, 0.74), the concentration of acetaminophen associated with 50% of the maximal drug effect (C 50, ACET ) 7.06 (95%CI 7.03, 7.72) mg/L, and the ibuprofen C 50 (C 50, IBU ) 3.95 (95%CI 2.57, 7.53) mg/L. The Hill coefficient was 1.48 (95%CI 0.92, 2.62) and an interaction term was fixed at zero (additivity). The half-time (t 1/2 keo) for equilibration between the plasma and effect site was 0.34 hour (95%CI 0.23, 1.98) for acetaminophen and 1.04 hour (95%CI 0.75, 1.77) for ibuprofen. Tramadol had a C 50, TRAM of 0.07 (95%CI 0.048, 1.07) mg/L with a t 1/2 keo, TRAM 1.78 hour (95%CI 1.06, 1.96)., Conclusion: Ibuprofen has an EC 50 for analgesia in children similar to that of adults (3.95 mg/L; 95%CI 2.57-7.53, vs 5-10 mg/L adults). The maximum effect from combination therapy (ie, 65% reduction in pain score) achieves satisfactory analgesia with commonly used doses but increased dose adds little additional benefit. The addition of tramadol to this analgesic mixture prolongs analgesia duration., (© 2018 John Wiley & Sons Ltd.)

Background and Objective: Co-Crystal of Tramadol-Celecoxib (CTC), in development for the treatment of moderate to severe acute pain, is a first-in-class co-crystal containing a 1:1 molecular ratio of two active pharmaceutical ingredients; rac-tramadol·HCl and celecoxib. This randomised, open-label, crossover study compared the bioavailability of both components after CTC administration under fed and fasting conditions., Methods: Healthy adults received single doses of 200 mg CTC under both fed and fasting conditions (separated by a 7-day washout). Each dose of CTC was administered orally as two 100 mg tablets, each containing 44 mg tramadol·HCl and 56 mg celecoxib. In the fed condition, a high-fat, high-calorie meal [in line with recommendations by the US Food and Drug Administration (FDA)] was served 30 min before CTC administration. Tramadol, O-desmethyltramadol and celecoxib plasma concentrations were measured pre- and post-dose up to 48 h. Pharmacokinetic parameters were calculated using non-compartmental analysis. Safety was also assessed., Results: Thirty-six subjects (18 female/18 male) received one or both doses of CTC; 33 provided evaluable pharmacokinetic data under fed and fasting conditions. For tramadol and O-desmethyltramadol, fed-to-fasting ratios of geometric least-squares means and corresponding 90% confidence interval (CI) values for maximum plasma concentration (C max ) and extrapolated area under the plasma concentration-time curve to infinity (AUC ∞ ) were within the pre-defined range for comparative bioavailability (80-125%). For celecoxib, C max and AUC ∞ fed-to-fasting ratios (90% CIs) were outside this range, at 130.91% (116.98-146.49) and 129.34% (121.78-137.38), respectively. The safety profile of CTC was similar in fed and fasting conditions., Conclusions: As reported for standard-formulation celecoxib, food increased the bioavailability of celecoxib from single-dose CTC. Food had no effect on tramadol or O-desmethyltramadol bioavailability., Clinical Trial Registration Number: 152052 (registered with the Therapeutic Products Directorate of Health Canada).

Four randomized, double-blind, placebo-controlled, 4-period drug-drug interaction studies were conducted in healthy subjects to evaluate the pharmacokinetic and pharmacodynamic (PD) interactions between mirogabalin and commonly used central nervous system depressants. Mirogabalin or placebo was administered alone or with single-dose lorazepam, zolpidem, tramadol, ethanol, or interacting drug placebo. Safety was assessed and serial samples for pharmacokinetic parameters were collected for up to 48 hours postdose. PD assessments included body sway (except tramadol), digit symbol substitution test, vertigo symptom scale short form, brief ataxia rating scale, and the Bond and Lader visual analog scale. Coadministration of mirogabalin with any of the 4 drugs did not cause any clinically relevant pharmacokinetic interactions. Peak mirogabalin concentration decreased by 28% (least squares mean ratio, 0.72; 90% confidence interval, [CI] 0.67, 0.76) following tramadol coadministration, and increased by 20% (least squares mean ratio, 1.20; 90%CI, 1.12, 1.28) following ethanol coadministration. Mirogabalin alone had little to no effect on PD parameters, but coadministration of mirogabalin with either lorazepam or ethanol increased the PD effects in body sway and digit symbol substitution test assays. Mirogabalin/lorazepam and mirogabalin/zolpidem increased occurrence of somnolence. Increased incidence of nausea and headache was noted with mirogabalin/tramadol and mirogabalin/ethanol, respectively., (© 2018, The American College of Clinical Pharmacology.)

Background: Seizure is one of the important symptoms of tramadol poisoning, but its causes are still unknown. The aim of this study is to find a relationship between tramadol and the concentrations of its metabolites versus the incidence of seizures following the consumption of high doses of tramadol., Methods: For this purpose, the blood samples of 120 tramadol-intoxicated patients were collected. The patients were divided in two groups (seizure and non-seizure). The concentrations of tramadol and its metabolites (M1, M2 and M5) were measured by using a high-performance liquid chromatography method. The relationship between tramadol and the levels of its metabolites and seizure incidences was also investigated., Results: In 72% of the patients, seizures occurred in the first 3 h after the ingestion of tramadol. The seizure incidences were significantly correlated with the patients' gender, concentrations of tramadol, M1 and M2 and the history of previous seizures (p<0.001). The average concentration of M2 was significantly higher in males (p=0.003). A previous history of the use of sedative-hypnotics and the co-ingestion of benzodiazepines and other opioids were shown to significantly decrease the rate of seizure. The rate of seizure was directly related to the concentrations of tramadol and its metabolites. Higher M2 concentration in males can be considered a reason for increased incidences of seizures in males. The plasma concentration of M1 affected the onset of seizure., Conclusions: Therefore, it can be concluded that differences in the levels of the metabolites can affect the threshold of seizure in tramadol-intoxicated patients.

Objective: 1) To determine the pharmacokinetics of tramadol hydrochloride and its active metabolite, O-desmethyltramadol (M1), after administration through different routes in female and male C57Bl/6 mice; 2) to evaluate the stability of tramadol solutions; and 3) to identify a suitable dose regimen for prospective clinical analgesia in B6 mice., Study Design: Prospective, randomized, blinded, parallel design., Animals: A total of 18 male and 18 female C57Bl/6 mice (20-30 g)., Methods: Mice were administered 25 mg kg -1 tramadol as a bolus [intravenously (IV), intraperitoneally (IP), subcutaneously (SQ), orally per gavage (OS gavage )] over 25 hours [orally in drinking water (OS water ) or Syrspend SF (OS Syrsp )]. Venous blood was sampled at six predetermined time points over 4 to 31 hours, depending on administration route, to determine tramadol and M1 plasma concentrations (liquid chromatography and tandem mass spectrometry detection). Pharmacokinetic parameters were described using a noncompartmental model. The stability of tramadol in water (acidified and untreated) and Syrspend SF (0.20 mg mL -1 ) at ambient conditions for 1 week was evaluated., Results: After all administration routes, C max was >100 ng mL -1 for tramadol and >40 ng mL -1 for M1 (reported analgesic ranges in man) followed by short half-lives (2-6 hours). The mean tramadol plasma concentration after self-administration remained >100 ng mL -1 throughout consumption time. M1 was found in the OS Syrs group only at 7 hours, whereas it was detectable in OS water throughout administration. Tramadol had low oral bioavailability (26%). Short-lasting side effects were observed only after IV administration. Water and Syrspend SF solutions were stable for 1 week., Conclusions and Clinical Relevance: 1) At the dose administered, high plasma concentrations of tramadol and M1 were obtained, with half-life depending on the administration route. 2) Plasma levels were stable over self-consumption time. 3) Solutions were stable for 1 week at ambient conditions., (Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Tramadol is administered to dogs for analgesia but has variability in its extent of absorption, which may hinder its efficacy. Additionally, the active opioid metabolite (M1) occurs in low concentrations. The purpose of this study was to determine if administration of oral tramadol with suspected metabolism inhibitors (ketoconazole, cimetidine) would lead to improved bioavailability of tramadol and M1. Six healthy Greyhounds were included. They were administered tramadol orally and intravenously, M1 intravenously, oral tramadol with oral ketoconazole and oral tramadol with oral cimetidine. Oral tramadol bioavailability was low (2.6%). Ketoconazole and cimetidine significantly increased tramadol bioavailability to 18.2% and 20.3%, respectively. The mean maximum plasma concentration of tramadol alone was 22.9 ng/ml, and increased to 109.9 and 143.2 μg/ml with ketoconazole and cimetidine, respectively. However, measured tramadol plasma concentrations were below the minimum concentration considered effective in humans (228 μg/ml). In all treatment groups, measured M1 concentrations (<7 μg/ml) were below concentrations associated with efficacy in humans. To conclude, tramadol and M1 concentrations were low and variable in dogs after oral dosing of tramadol, even in combination with cimetidine or ketoconazole, but effective concentrations in dogs have not been defined., (© 2017 John Wiley & Sons Ltd.)

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief following concerns raised by a reader. The particles shown in Fig. 3F appear to be copies of each other as they share the identical arrangement of the characteristic speckles inside the particles. In addition, the extraordinary similarities observed between the data presented in Fig. 4C and in Fig. 3C in ACS Biomater. Sci. Eng., 2017, 3 (9), pp 2120–2135, 10.1021/acsbiomaterials.7b00089, Fig. 4A in Colloids and Surfaces B: Biointerfaces, Volume 142, 1 June 2016, Pages 248-258 10.1016/j.colsurfb.2016.02.053 and Fig. 1D in Biosensors and Bioelectronics, Volume 73, 15 November 2015, Pages 234-244, 10.1016/j.bios.2015.06.005 are highly unlikely. The problems with the data presented cast doubt on all the data, and accordingly also the conclusions based on that data, in this publication. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Rationale: Several opioid analgesics have been related to the prolongation of cardiac repolarization, a condition which can be fatal. In order to establish a correct estimation of the risk/benefit balance of therapeutic doses of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene, it was necessary to develop an analytical method to determinate plasma concentrations of these opioids., Methods: Here we describe a method which incorporates strong alkaline treatment to obtain norpropoxyphene amide followed by a one-elution step solid-phase extraction, and without further derivatization. Separation and quantification were achieved by gas chromatography/electron ionization mass spectrometry (GC/EI-MS) in selected-ion monitoring mode. Quantification was performed with 500 μL of plasma by the addition of deuterated analogues as internal standards., Results: The proposed method has been validated in the linearity range of 25-1000 ng/mL for all the analytes, with correlation coefficients higher than 0.990. The lower limit of quantification was 25 ng/mL. The intra- and inter-day precision, calculated in terms of relative standard deviation, were 2.0-12.0% and 6.0-15.0%, respectively. The accuracy, in terms of relative error, was within a ± 10% interval. The absolute recovery and extraction efficiency ranged from 81.0 to 111.0% and 81.0 to 105.0%, respectively., Conclusions: A GC/MS method for the rapid and simultaneous determination of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene in human plasma was developed, optimized and validated. This procedure was shown to be sensitive and specific using small specimen amounts, suitable for application in routine analysis for forensic purposes and therapeutic monitoring. To our knowledge, this is the first full validation of the simultaneous determination of these opioids and their metabolites in plasma samples., (Copyright © 2017 John Wiley & Sons, Ltd.)

Systemic arterial hypertension is a major risk factor for cerebrovascular disease. Therefore, adequate control of blood pressure is of enormous importance. One of the many fixed-dose single-pill antihypertensive formulations available on the market is the combination of nebivolol and hydrochlorothiazide. The objective of this study was to develop two distinct high-performance liquid chromatography coupled to tandem mass spectrometry methods to simultaneously quantify nebivolol and hydrochlorothiazide in human plasma. The methods were employed in a bioequivalence study, the first assay involving a nebivolol fixed-dose single-pill formulation based on healthy Brazilian volunteers. Nebilet HCT™ (nebivolol 5 mg + hydrochlorothiazide 12.5 mg tablet, manufactured by Menarini) was the test formulation. The reference formulations were Nebilet™ (nebivolol 5 mg tablet, manufactured by Menarini) and Clorana™ (hydrochlorothiazide 25 mg tablet, manufactured by Sanofi). For both analytes, liquid-liquid extraction was employed for sample preparation and the chromatographic run time was 3.5 min. The limits of quantification validated were 0.02 ng/mL for nebivolol and 1 ng/mL for hydrochlorothiazide. Since the 90% CI for C max , AUC (0-last) and AUC (0-inf) individual test/reference ratios were within the 80-125% interval indicative of bioequivalence, it was concluded that Nebilet HCT™ is bioequivalent to Nebilet™ and Clorana™., (Copyright © 2016 John Wiley & Sons, Ltd.)

Drug testing is a useful tool to identify drug use or monitor adherence to prescription drugs. The interpretation of drug results can be complicated based on the pattern and proportional concentrations of drugs and/or drug metabolite(s). The purpose of this retrospective study was to detect the positivity rates and metabolic patterns of five prescription drugs, including fentanyl, meperidine, methylphenidate, tapentadol and tramadol. Retrospective data were retrieved from the laboratory information system in a national reference laboratory. Drug testing was performed using four mass spectrometry methods that were validated for clinical use. For urine specimens, the positivity rate was the highest for methylphenidate (62.3%, n = 2,489), followed by tramadol (43.7%, n = 3,483), fentanyl (41.9%, n = 4,657), tapentadol (37.9%, n = 736) and meperidine (8.3%, n = 138). Among positive samples, both parent drug and metabolite(s) was detectable in 94.9% of meperidine samples, 94.5% of tramadol samples, 93.8% of fentanyl samples, 89.9% of methylphenidate and 86.6% of tapentadol samples. For serum or plasma specimens, the positivity rate was the highest for tapentadol (75.0%, n = 39), followed by methylphenidate (74.2%, n = 569), fentanyl (53.6%, n = 113), meperidine (41.9%, n = 18) and tramadol (28.9%, n = 213). Similar metabolic patterns were found in serum or plasma. Of positive results, both parent drug and metabolite(s) were found in 94.7% of fentanyl samples, 83.3% of meperidine samples, 79.6% of methylphenidate samples, 53.8% of tapentadol samples and 44.1% of tramadol samples. Our data demonstrates the metabolic patterns of five drugs from a random urine or serum/plasma collection in patients that have been prescribed these medications. The data presented can be used to guide clinicians in determining drug adherence by assessing the positivity rates of the parent drug and corresponding metabolite(s)., (© The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Tramadol is a weak opioid analgesic indicated for the treatment of moderate to severe pain. Tramadol intoxication can be lethal, and this drug is frequently involved in voluntary overdose. Classically, tramadol intoxication is associated with neurological and respiratory side effects. In contrast, cardiac effects are poorly documented in the literature. We report a case of severe tramadol intoxication, with plasma concentration 20 times the toxic threshold, complicated by refractory cardiogenic shock, successfully treated by extra corporeal life support (ECLS) with a favorable cardiac outcome and ECLS weaning at day 10. Seizure, clonus, and nonreactive mydriasis were present during 4 days, and complete awakening was delayed to day 15. Poisoning caused by high doses of tramadol can lead to refractory cardiogenic shock, and ECLS can be considered as effective rescue therapy in this context.

Objective: The aim of the study was to evaluate the influence of tramadol on acute nociception in dogs., Study Design: Experimental, blinded, randomized, crossover study., Animals: Six healthy laboratory Beagle dogs., Methods: Dogs received three treatments intravenously (IV): isotonic saline placebo (P), tramadol 1 mg kg -1 (T1) and tramadol 4 mg kg -1 (T4). Thermal thresholds were determined by ramped contact heat stimulation (0.6 °C second -1 ) at the lateral thoracic wall. Mechanical thresholds (MT) were measured using a probe containing three blunted pins which were constantly advanced over the radial bone, using a rate of force increase of 0.8 N second -1 . Stimulation end points were defined responses (e.g. skin twitch, head turn, repositioning, vocalization) or pre-set cut-out values (55 °C, 20 N). Thresholds were determined before treatment and at predetermined time points up to 24 hours after treatment. At each measurement point, blood was collected for determination of O-desmethyltramadol concentrations. The degree of sedation and behavioural side effects were recorded. Data were analysed by one-way anova and two-way anova for repeated measurements., Results: Thermal nociception was not influenced by drug treatment. Mechanical nociception was significantly increased between P and T1 at 120 and 240 minutes, and between P and T4 at 30, 60, 240 and 420 minutes. T1 and T4 did not differ. O-desmethyltramadol (M1) maximum plasma concentrations (C max ) were 4.2±0.8 ng mL -1 and 14.3±2.8 ng mL -1 for T1 and T4, respectively. Times to reach maximum plasma concentrations (T max ) were 27.6±6.3 minutes for T1 and 32.1±7.8 minutes for T4. No sedation occurred. There were signs of nausea and mild to moderate salivation in both groups., Conclusion and Clinical Relevance: Tramadol was metabolized marginally to O-desmethyltramadol and failed to produce clinically relevant acute antinociception. Therefore, the use of tramadol for acute nociceptive pain is questionable in dogs., (Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

The organic cation transporter OCT1 (SLC22A1) mediates uptake and metabolism of the active tramadol metabolite (+)O-desmethyltramadol in the liver. In this study, the influence of OCT1 genetic polymorphisms on pharmacokinetics and analgesic efficacy of tramadol in patients recovering from surgery was analyzed in addition to the CYP2D6 genotype. Postoperative patients who received tramadol through patient-controlled analgesia were enrolled. Genotypes resulting in 0, 1, or 2 active OCT1 alleles were determined as well as CYP2D6 genotypes. The primary endpoint was the 24-hour postoperative tramadol consumption in patients with 0 vs at least 1 active OCT1 allele. Secondary endpoint was the OCT1-dependent plasma concentration (areas under the concentration-time curves) of the active tramadol metabolite (+)O-desmethyltramadol. Of 205 patients, 19, 82, and 104 carried 0, 1, and 2 active OCT1 alleles, respectively. Cumulative tramadol consumption through patient-controlled analgesia was lowest in patients with 0 active OCT1 allele compared with the group of patients with 1 or 2 active alleles (343 ± 235 vs 484 ± 276 mg; P = 0.03). Multiple regression revealed that the number of active OCT1 alleles (P = 0.014), CYP2D6 (P = 0.001), pain scores (P < 0.001), and the extent of surgery (0.034) had a significant influence on tramadol consumption. Plasma areas under the concentration-time curves of (+)O-desmethyltramadol were 111.8 (95% confidence interval: 63.4-160.1), 80.2 (65.1-95.3), and 64.5 (51.9-77.2) h·ng·mL in carriers of 0, 1, or 2 active OCT1 alleles (P = 0.03). Loss of OCT1 function resulted in reduced tramadol consumption and increased plasma concentrations of (+)O-desmethyltramadol in patients recovering from surgery. Therefore, analyzing OCT1 next to CYP2D6 genotype might further improve future genotype-dependent dose recommendations for tramadol.

Tramadol hydrochloride is a centrally acting analgesic used for the treatment of moderate-to-severe pain. It has three main metabolites: O-desmethyltramadol (M1), N-desmethyltramadol (M2), and N,O-didesmethyltramadol (M5). Because of the frequent use of tramadol by patients and drug abusers, the ability to determine the parent drug and its metabolites in plasma and cerebrospinal fluid is of great importance. In the present study, a pharmacokinetic approach was applied using two groups of five male Wistar rats administered a 20mg/kg dose of tramadol via intravenous (i.v.) or intraperitoneal (i.p.) routes. Plasma and CSF samples were collected at 5-360min following tramadol administration. Our results demonstrate that the plasma values of Cmax (C0 in i.v. group) and area under the curve (AUC)0-t for tramadol were 23,314.40±6944.85 vs. 3187.39±760.25ng/mL (Cmax) and 871.15±165.98 vs. 414.04±149.25μg·min/mL in the i.v. and i.p. groups, respectively (p<0.05). However, there were no significant differences between i.v. and i.p. plasma values for tramadol metabolites (p>0.05). Tramadol rapidly penetrated the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB) (5.00±0.00 vs. 10.00±5.77min in i.v. and i.p. groups, respectively). Tramadol and its metabolites (M1 and M2) were present to a lesser extent in the cerebrospinal fluid (CSF) than in the plasma. M5 hardly penetrated the CSF, owing to its high polarity. There was no significant difference between the AUC0-t of tramadol in plasma (414.04±149.25μg·min/mL) and CSF (221.81±83.02μg·min/mL) in the i.p. group. In addition, the amounts of metabolites (M1 and M2) in the CSF showed no significant differences following both routes of administration. There were also no significant differences among the Kp,uu,CSF(0-360) (0.51±0.12 vs. 0.63±0.04) and Kp,uu,CSF(0-∞) (0.61±0.10 vs. 0.62±0.02) for i.v. and i.p. pathways, respectively (p>0.05). Drug targeting efficiency (DTE) values of tramadol after i.p. injection were more than unity for all scheduled time points. Considering the main analgesic effect of M1, it is hypothesized that both routes of administration may produce the same amount of analgesia., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Tramadol concentrations and analgesic effect are dependent on the CYP2D6 enzymatic activity. It is well known that some genetic polymorphisms are responsible for the variability in the expression of this enzyme and in the individual drug response. The detection of allelic variants described as non-functional can be useful to explain some circumstances of death in the study of post-mortem cases with tramadol. A Sanger sequencing methodology was developed for the detection of genetic variants that cause absent or reduced CYP2D6 activity, such as *3, *4, *6, *8, *10 and *12 alleles. This methodology, as well as the GC/MS method for the detection and quantification of tramadol and its main metabolites in blood samples was fully validated in accordance with international guidelines. Both methodologies were successfully applied to 100 post-mortem blood samples and the relation between toxicological and genetic results evaluated. Tramadol metabolism, expressed as its metabolites concentration ratio (N-desmethyltramadol/O-desmethyltramadol), has been shown to be correlated with the poor-metabolizer phenotype based on genetic characterization. It was also demonstrated the importance of enzyme inhibitors identification in toxicological analysis. According to our knowledge, this is the first study where a CYP2D6 sequencing methodology is validated and applied to post-mortem samples, in Portugal. The developed methodology allows the data collection of post-mortem cases, which is of primordial importance to enhance the application of these genetic tools to forensic toxicology and pathology., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Reasons for Performing Study: Laminitis is a painful disease for which adequate pain management remains a challenging and largely unmet medical need., Objectives: To investigate plasma concentrations, analgesic and physiological effects of 2 doses of tramadol in horses with chronic laminitis., Study Design: Nonrandomised trial., Methods: Four horses with naturally occurring chronic laminitis received 5 mg/kg bwt and then 10 mg/kg bwt tramadol orally every 12 h for one week with a one-week washout between. Noninvasive arterial blood pressure, heart and respiratory rates, intestinal sounds and forelimb off-loading frequency were evaluated before and during treatments. Plasma tramadol and metabolite (M1 and M2) concentrations were measured on predetermined days and times after the morning dosing., Results: Forelimb off-loading frequency decreased significantly with 10 mg/kg bwt (40%, P = 0.02) but not with 5 mg/kg bwt (9%, P = 0.4). Physiological variables did not change significantly with either treatment. For 5 and 10 mg/kg bwt treatments, respectively, individual maximum plasma concentrations (μg/l) ranged from 329 to 728 and 628 to 1330 (tramadol), 12-24 and 32-80 (M1), and 90-157 and 239-362 (M2). Respective median area under the concentration vs. time curves (h μg/l) were 727 and 1426, 33 and 88, 303 and 1003., Conclusions: Twice daily oral tramadol at 10 mg/kg bwt may produce analgesic plasma levels in horses with chronic laminitis., (© 2015 EVJ Ltd.)

This study aimed to compare the pharmacokinetics of tramadol between young and middle-aged dogs. Tramadol (4 mg/kg) was administered intravenously (IV) to young and middle-aged dogs (2 and 8-10 years, respectively). Plasma concentrations of tramadol were measured using high-performance liquid chromatography (HPLC), and its pharmacokinetics best fit a two-compartment model. The volume of distribution (Vd), elimination half-life (t1/2,β) and total body clearance (CLtot) of the young group were 4.77 ± 1.07 l/kg, 1.91 ± 0.26 hr and 29.9 ± 7.3 ml/min/kg, respectively, while those of the middle-aged group were 4.73 ± 1.43 l/kg, 2.39 ± 0.97 hr and 23.7 ± 5.4 ml/min/kg, respectively. Intergroup differences in the t1/2,β and CLtot were significant (P<0.05). In conclusion, tramadol excretion was significantly prolonged in middle-aged dogs.

The analgesic drug tramadol and its metabolites are chiral compounds, with the (+)- and (-)-enantiomers showing different pharmacological and toxicological effects. This novel enantioselective method, based on LC-MS/MS in reversed phase mode, enabled measurement of the parent compound and its three main metabolites O-desmethyltramadol, N-desmethyltramadol and N,O-didesmethyltramadol simultaneously. Whole blood samples of 0.5g were fortified with internal standards (tramadol-(13)C-D3 and O-desmethyl-cis-tramadol-D6) and extracted under basic conditions (pH 11) by liquid-liquid extraction. Chromatography was performed on a chiral alpha-1-acid glycoprotein (AGP) column preceded by an AGP guard column. The mobile phase consisted of 0.8% acetonitrile and 99.2% ammonium acetate (20mM, pH 7.2). A post-column infusion with 0.05% formic acid in acetonitrile was used to enhance sensitivity. Quantitation as well as enantiomeric ratio measurements were covered by quality controls. Validation parameters for all eight enantiomers included selectivity (high), matrix effects (no ion suppression/enhancement), calibration model (linear, weight 1/X(2), in the range of 0.25-250ng/g), limit of quantitation (0.125-0.50ng/g), repeatability (2-6%) and intermediate precision (2-7%), accuracy (83-114%), dilution integrity (98-115%), carry over (not exceeding 0.07%) and stability (stable in blood and extract). The method was applied to blood samples from a healthy volunteer administrated a single 100mg dose and to a case sample concerning an impaired driver, which confirmed its applicability in human pharmacokinetic studies as well as in toxicological and forensic investigations., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Unlabelled: In recent years, several cases of torsade de pointes have been associated with many opioids. However, to present no cases have been reported with tramadol., Objective: To evaluate the effect of tramadol on QT-interval in the clinical setting., Research Design and Methods: Medical history and comorbidities predisposing to QT interval prolongation were registered for patients requiring medical assistance that involved tramadol administration. Ionograms and ECGs were performed at baseline and intratreatment; QT interval was analyzed after correction with Bazzet, Fridericia, Framinghan and Hogdes formula., Results: 115 patients were studied (50.4% males) All patients had received tramadol 150-400 mg/day during 3.0-5.0 days at the moment of intratreatment control. Plasma concentrations of tramadol were 201-1613 ng/mL. Intratreatment electrocardiographic control, as mean ± SD (range), showed QTcB 372±32 (305 to 433), QTcFri 356±37 (281 to 429), QTcFra 363±33 (299 to 429), QTcH 362±30 (304 to 427), ΔQTcB 26±40 (-73 to 110), ΔQTcFri 24±48 (-97 to 121), ΔQTcFra 22±42 (-81 to 109) and .QTcH 22±38 (-68 to 110) ms. QTc interval presents high correlation with plasma tramadol concentrations (for .QTc, R>0.77). Renal failure was associated with a relative risk for ΔQTc > 30 ms of 1.90 (IC95% 1.31-2.74) and for ΔQTc > 60 ms of 4.74 (IC95% 2.57-8.74). No patient had evidence of arrhythmia during the present study., Conclusion: Tramadol produces QTc interval prolongation in good correlation with plasma drug concentrations; renal failure is a risk factor for higher concentration and QT prolongation by tramadol.

Reasons for Performing Study: Tramadol is an analgesic agent used in man and a number of veterinary species. The pharmacokinetics and behavioural effects of tramadol and its active metabolite have been described in mature horses, but not in young foals., Objectives: To characterise the pharmacokinetics, metabolism and some induced behavioural and physiological responses following i.v. tramadol administration in the same group of foals on 4 different occasions, from a few days after birth to age 43 days., Study Design: Experimental., Methods: Tramadol was administered i.v. (3 mg/kg bwt) to a group of 8 foals on 4 separate occasions at ages 6–8, 13–15, 20–22 and 40–43 days. Blood samples were collected prior to administration and at multiple times until 48 h post administration. Blood samples were analysed for tramadol and metabolite concentrations and pharmacokinetics determined at each age. Behavioural and physiological effects were also assessed., Results: The average volume of distribution was 5.10, 4.63, 4.02 and 3.84 l/kg bwt and clearance 3.44, 3.08, 3.14 and 2.69 l/h/kg bwt when foals were aged 6–8, 13–15, 20–22 and 40–43 days, respectively. There was not a significant difference in the elimination half-life between age groups (1.52, 1.73, 1.13 and 1.51 for ages 6–8, 13–15, 20–22 and 40–43 days, respectively). The metabolites produced were the same as in mature horses; however, glucuronidation capability, appeared to increase with increasing age. Tramadol administration was well tolerated at all ages studied with sedation noted in the 3 older age groups., Conclusions: Tramadol appears to be consistently well tolerated following i.v. administration of 3 mg/kg bwt to foals ranging in age from 1 to 6 weeks. Although analgesic concentrations in foals have yet to be established, the results of this study support further study of tramadol for clinical use in foals.

Ambiguous findings during external examination of a deceased in combination with dubious autopsy findings can raise doubts concerning the manner and cause of death. We report the case of a 35-year-old female deceased who had suffered from a borderline personality and depressive disorder with suicidal ideation. At the death scene, the body showed massive facial swelling accompanied by complete reddening of the skin of the face, with patchy skin abrasions on the forehead and neck, and purple bruise-like discolorations distributed symmetrically over both shoulders, elbows, hands, hips, knees, lower legs, and feet, raising the suspicion of underlying massive external blunt force injury. Police investigators strongly suspected sexual homicide. At autopsy, dissection in layers revealed massive subcutaneous hemorrhages as the cause of the reddish skin discolorations. Toxicological analyses showed fatal levels of lamotrigine with additional proof of zopiclone, zolpidem, diphenhydramine, O-desmethylvenlafaxine, pregabalin, tramadol, and modafinil in venous blood. Histologically, both the macroscopically impressive purple skin changes with underlying bleeding into the subcutaneous tissue and the skin abrasions were due to leukocytoclastic vasculitis, a form of acute hypersensitivity vasculitis that was a reaction to the multiple therapeutic drugs that the woman had taken shortly before death. The manner of death was classified as suicide, and sexual homicide was ruled out.

Exhaled breath (EB) is a promising matrix for bioanalysis of non-volatiles and has been routinely implemented for drugs of abuse analysis. Nothing is known regarding the pharmacokinetics of therapeutics and their metabolites in EB. Therefore, we used tramadol as a model drug. Twelve volunteers received a single oral dose of tramadol and repeated sampling of EB, plasma, and oral fluid (OF) was done for 48 h using a particle filter device for EB and the Quantisal-device for OF. Samples were analyzed with LC-MS/MS and the pharmacokinetic correlations between matrices were investigated. The initial tramadol half-life in EB was shorter than in plasma but it reappeared in EB after 8-24 h. The ratio of O-desmethyltramadol to tramadol was considerably lower in EB and OF compared to plasma. This pilot study compared for the first time the pharmacokinetics of a therapeutic drug and active metabolite in different biomatrices including EB and demonstrated its potential for bioanalysis., (Copyright © 2015 Elsevier Inc. All rights reserved.)

In reptiles, administration of opioid drugs has yielded unexpected results with respect to analgesia. The aims of this study were to assess the pharmacokinetic/pharmacodynamic (PK/PD) properties of tramadol and its active metabolite M1 and to evaluate the effect of the renal portal system on the PK/PD parameters in yellow-bellied slider turtles. Turtles (n = 19) were randomly assigned to four treatment groups, according to a masked, single-dose, four-treatment, unpaired, four-period crossover design. Group A (n = 5) received a single i.m. dose of tramadol (50 mg/mL) at 10 mg/kg in the proximal hindlimb. Group B (n = 5) received the same i.m. dose but in the forelimb. Groups C (n = 5) and D (n = 4) received a single i.m. injection of saline (NaCl 0.9%) of equivalent volume to the volumes of tramadol injected in the hind- and forelimb, respectively. Groups were rotated (1-month washout period) until the completion of the crossover study. Tramadol plasma concentrations were evaluated by a validated HPLC-FL method. An infrared thermal stimulus was applied to the plantar surface of the turtles' hindlimbs to evaluate the thermal withdrawal latency (TWL). The two PK profiles of tramadol differed in the first 2 h following administration, but overlapped in the elimination phases. The metabolite M1 was formed in both the treatment groups, showing similar pharmacokinetic trends, although the amount of M1 was significantly higher (20%) in the hindlimb vs. forelimb group. Turtles given tramadol in the hind- and forelimb showed a significant increase in TWL over the periods of 0.5-48 and 8-48 h, respectively. The calculated % maximal possible response (% MPR) was low (about 24%). The PK/PD correlations between M1 plasma concentrations vs. % MPR appeared to show a counterclockwise hysteresis loop shape., (© 2015 John Wiley & Sons Ltd.)

Tramadol is a centrally acting opioid analgesic that is prone to polymorphic metabolism via cytochrome P450 (CYP) 2D6. The generation of the active metabolite, O-desmethyltramadol, which occurs through the CYP 2D6 pathway, significantly contributes to the drug's activity. However, dosage adjustments of tramadol are typically not practiced in the clinic when treating patients who are homozygous extensive metabolizers, heterozygous extensive metabolizers, or poor metabolizers. In the event of a tramadol overdose, the consequences may be influenced importantly by the genotype or phenotype status of the subject. Depending on the individual subject's CYP 2D6 status, one may see excessive miotic-related toxicity driven by the excessive availability of O-desmethyltramadol or one may manifest mydriatic-related toxicity driven by the excessive availability of tramadol. This report provides pharmacokinetic perspectives in situations of tramadol overdosing.

Tramadol is a synthetic, centrally acting, opiate-like analgesic that is structurally related to codeine and morphine. The objective of this study was to determine the pharmacokinetics of tramadol hydrochloride and its major active metabolite O-desmethyltramadol (M1) in the California sea lion (Zalophus californianus). A single dose of tramadol was administered orally in fish at 2 mg/kg to a total of 15 wild California sea lions admitted for rehabilitation. Twenty-four total blood samples were collected post drug administration at 10, 20, 30, and 45 min and at 1, 3, 5, 6, 8, 12, and 24 hr. Blood plasma was separated and stored at -80°C until analysis with high-performance liquid chromatography was performed to determine levels of tramadol and M1, the major active metabolite. The results indicate that the plasma levels of parent tramadol are low or negligible during the first 30-45 min and then reach the predicted mean maximum plasma concentration of 358 ng/ml at 1.52 hr. The M1 metabolite was not detectable in 21 of 24 plasma samples, below the level of quantification of 5 ng/ml in one sample, and detectable at 11 and 17 ng/ml in two of the samples. This study suggests that a 2 mg/kg dose would need to be administered every 6-8 hr to maintain concentrations of tramadol above the minimum human analgesic level for mild to moderate pain. Based on dosing simulations, a dose of 4 mg/kg q8 hr or q12 hr, on average, may represent an adequate compromise, but further studies are needed using a larger sample size. Pharmacodynamic studies are warranted to determine if tramadol provides analgesic effects in this species. The potential for tramadol toxicosis at any dose also has not been determined in this species.