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Lisofylline (LSF), is the R-(−) enantiomer of the metabolite M1 of pentoxifylline, and is currently under development for the treatment of type 1 diabetes. The aim of the study was to develop a physiologically based pharmacokinetic (PBPK) model of LSF in mice and to perform simulations in order to predict LSF concentrations in human serum and tissues following intravenous and oral administration. The concentrations of LSF in serum, brain, liver, kidneys, lungs, muscle, and gut were determined at different time points over 60 min by a chiral HPLC method with UV detection following a single intravenous dose of LSF to male CD-1 mice. A PBPK model was developed to describe serum pharmacokinetics and tissue distribution of LSF using ADAPT II software. All pharmacokinetic profiles were fitted simultaneously to obtain model parameters. The developed model characterized well LSF disposition in mice. The estimated intrinsic hepatic clearance was 5.427 ml/min and hepatic clearance calculated using the well-stirred model was 1.22 ml/min. The renal clearance of LSF was equal to zero. On scaling the model to humans, a good agreement was found between the predicted by the model and presented in literature serum LSF concentration–time profiles following an intravenous dose of 3 mg/kg. The predicted LSF concentrations in human tissues following oral administration were considerably lower despite the twofold higher dose used and may not be sufficient to exert a pharmacological effect. In conclusion, the mouse is a good model to study LSF pharmacokinetics following intravenous administration. The developed PBPK model may be useful to design future preclinical and clinical studies of this compound.

We assessed the relations between MPA, free MPA (fMPA) and MPA glucuronide (MPAG) pharmacokinetics and the clinical condition of renal transplant recipients treated with EC-MPS and tacrolimus (Tac) in the first post-transplant year. In 18 adult patients blood samples were collected up to 12 h after EC-MPS oral administration. EC-MPS metabolites’ plasma concentrations were determined using validated HPLC methods. All patients reached MPA area under the time–concentration curve (AUC0–12) above 30 µg h/mL. Most of the MPA, fMPA and all MPAG concentrations correlated significantly with respective AUC0–12 values. Some fMPA and all MPAG pharmacokinetic parameters correlated negatively with creatinine clearance and positively with creatinine concentration, whereas no such correlation was observed for MPA. Lower hemoglobin concentrations were observed in patients with higher MPA or fMPA C 0. The significant correlations between MPA C 3 as well as MPA C 4 and MPA AUC0–4 and MPA AUC0–12 may be of importance in further studies including larger number of patients in regard to establishing LSS. In patients treated with EC-MPS and Tac, monitoring MPA C 0 may be important, as too high MPA C 0 may contribute to anemia onset. In EC-MPS treated patients, MPAG concentration is related to renal function as MPAG pharmacokinetics were higher in patients with renal impairment.

Recombinant human follicle stimulating hormone (r-hFSH) is effective and safe for controlled ovarian stimulation. Bemfola(®) (Finox AG, Burgdorf, Switzerland), a new biosimilar r-hFSH, has proven comparable non-clinical pharmacological profiles to those of the widely used Gonal-f(®) (Serono Pharma S.p.A., Bari, Italy). The objective of this study was to show that Bemfola(®) yields comparable clinical pharmacokinetic (PK) and safety profiles to Gonal-f(®) in healthy female subjects. In this randomized, Phase I trial conducted in healthy female volunteers (N = 32), a 2-period, balanced 2-treatment crossover design was used. A single subcutaneous dose of 225 IU Bemfola(®) or Gonal-f(®) was administered in each treatment period per sequence. Blood was collected for pharmacokinetic analysis until 10 days after each r-hFSH treatment. For down-regulation of endogenous FSH subjects were given a depot injection with leuprolide acetate prior to the study drug in either sequence. Pharmacokinetic data was available for 23 subjects. No appreciable differences in key PK parameters were detected between the r-hFSH products as per non-compartmental PK analysis [i.e. for Bemfola(®) and Gonal-f(®) respectively AUC0-192 424.90 and 432.75 IU h/L, C max 0.98 and 0.95 IU/L, T max 24.0 h (range 6.0-24.0) and 24.0 h (range 9.0-24.0), t 1/2 43.58 h [standard deviation (SD 14.17)] and 42.58 h (SD 16.47), and K e 0.0075 1/h (SD 0.003) and 0.0077 1/h (SD 0.002)]. Subgroup analysis for estradiol (E2) response was similar for Bemfola(®) and Gonal f(®) (AUC(0--120) p = 0.21 and C max p = 0.82). No major safety issues were identified and no immunogenic reaction to r-hFSH was observed. The results of this study indicate that a single dose of Bemfola(®) exhibits pharmacokinetic and safety profiles comparable to Gonal-f(®) in healthy young women.

Ibandronate is a drug widely used outside Japan for the treatment of osteoporosis. It is available in formulations for intermittent intravenous (i.v.) administration and for intermittent (once monthly) oral administration. Ibandronate was recently approved in Japan as an i.v. injection with a dosing regimen of 1.0 mg once a month. To establish the optimal dose for oral administration of ibandronate in Japanese osteoporotic patients, we investigated the pharmacokinetics of and pharmacodynamic response to ibandronate following oral and intravenous administrations to Japanese subjects. Ibandronate (20, 50, 100, or 150 mg) was given orally to healthy postmenopausal Japanese women and to Japanese patients with primary osteoporosis. Serial measurements were obtained for the concentrations of serum ibandronate and urinary cross-linked C-telopeptide of Type I collagen (uCTX). Pharmacokinetic parameters and the time profiles of creatinine-corrected uCTX were compared with those obtained from postmenopausal Japanese women with osteopenia after administration of 1.0 mg i.v. ibandronate. Following oral administration of ibandronate, the area under the serum ibandronate concentration–time curve (AUCinf) increased dose-proportionally for doses up to 100 mg; at 150 mg, AUCinf increased beyond the dose-proportionality seen with doses up to 100 mg. The AUCinf within the linear range following administration of 100 mg oral ibandronate was similar to that following 1.0 mg i.v. ibandronate. Additionally, corrected uCTX decreased after administration of 100 mg oral ibandronate and remained decreased for 1 month; the magnitude of the decrease was similar to or greater than that obtained after 1.0 mg i.v. ibandronate. From a clinical pharmacological perspective, administration of 100 mg/month oral ibandronate was equivalent to that of 1.0 mg/month i.v. ibandronate. Electronic supplementary material The online version of this article (doi:10.1007/s13318-014-0242-5) contains supplementary material, which is available to authorized users.

Indacaterol is an inhaled, ultra-long-acting β2-agonist that provides 24-h bronchodilation with once-daily dosing in patients with chronic obstructive pulmonary disorder. This study evaluated the pharmacokinetics, safety, and tolerability of multiple daily inhaled doses of indacaterol 150 or 300 μg once daily in healthy Chinese volunteers. This was a single-center, randomized, double-blind, multiple-dose, parallel-group study, placebo-controlled trial including two doses of indacaterol: 150 and 300 μg. Serum indacaterol was quantified using high-performance liquid chromatography-mass spectrometry with a lower limit of quantification of 0.01 ng/mL. The pharmacokinetic parameters were analyzed using non-compartmental analysis and included C max, T max, and AUC0-24h on Day 1 and AUC0-24h,ss, C max,ss, C min,ss, C av,ss, T max,ss, T 1/2, T 1/2,acc, CL/F, V z/F, and R acc on Day 14 (after repeated once-daily doses). Safety analyses were recorded using physical examination, biochemical tests, and ECG. Indacaterol steady state was achieved after 12-14 days of daily dosing. The mean effective half-life of indacaterol (based on drug accumulation at steady state) was 33.9 and 35.8 h for 150 and 300 μg, respectively. Systemic exposure to indacaterol increased 1.27 and 1.34-fold between the 150- and 300-μg doses on Day 1 (first dose) and Day 14 (repeated dose), respectively. Indacaterol 150 and 300 μg were safe and well tolerated in these volunteers. The pharmacokinetics of multiple inhaled doses of indacaterol 150 and 300 μg (for 14 days) were consistent with moderate systemic accumulation at steady state after repeated once-daily inhalation in healthy Chinese volunteers.

To compare and evaluate the bioavailability for intravenous fosphenytoin sodium with that of intravenous phenytoin sodium in Japanese subjects. In study 1, healthy Japanese male volunteers received a 30-min infusion of 375 mg fosphenytoin sodium or an equimolar dose of 250 mg phenytoin by a double-blind, crossover method. In study 2, other healthy Japanese male volunteers received a 30-min or 10-min infusion of 563 mg fosphenytoin sodium, followed by a dose of 750 mg after 2 weeks in an unblinded manner. Comparing with 250 mg phenytoin sodium, 375 mg fosphenytoin sodium exhibited lower total plasma phenytoin C max, whereas the geometric mean ratio of the AUC of total and free phenyotoin for fosphenytoin sodium at a dose of 375 mg was very similar to phenytoin sodium at a equimolar dose of 250 mg (AUC0-t ratio: 0.98 and 1.02, respectively). Therefore, fosphenytoin is almost completely converted to phenytoin in subjects. Fosphenytoin sodium was rapidly converted to phenytoin at doses of 375, 563, and 750 mg. The maximum concentration (C max) of total plasma phenytoin increased in a dose-dependent manner. The area under the plasma concentration-time curve (AUC) increased slightly more than proportionally with the administered dose, and clearance (CL) decreased with increasing dose. Pain and other infusion-site reactions were reported by all 12 subjects with phenytoin sodium, whereas very few symptoms were observed with fosphenytoin sodium. In conclusion, fosphenytoin sodium is considered to be a useful substitute for phenytoin sodium with almost no associated injection-site reactions.

Pharmacokinetics of ketoprofen (KTP) enantiomers has been studied in patients with rheumatoid arthritis (RA) following administration of a single oral dose of 100 mg rac-KTP during multidrug therapy taking into consideration the genotype of RA patients Concentrations of (-)-R and (+)-S enantiomers of KTP in plasma, urine and synovial fluid samples were determined using a validated HPCE method. The genotype of the patients was analyzed using PCR-RFLP method to determine the polymorphic variants of genes coding CYP2C8 and CYP2C9 isoenzymes. The levels of KTP enantiomers in synovial fluid at 4 h following administration were insignificantly greater [(-)-R = 1.34 ± 0.91 mg/L; (+)-S = 1.38 ± 0.91 mg/L] than in plasma [(-)-R = 1.15 ± 0.95 mg/L; (+)-S = 1.22 ± 0.95 mg/L]. The values of AUC(0-∞) were 11.89 ± 5.00 and 10.92 ± 4.10 mg h/L for (-)-R and (+)-S enantiomer, respectively, and were lower compared with data obtained in healthy volunteers following administration of the same dose of rac-KTP. But, no statistically significant differences were observed also for C (max), Cl, V (d), t (0.5) and MRT of KTP enantiomers. The total percentage of unchanged KTP eliminated with urine of RA patients was in the range of 30-50% of the administered dose. Though RA patients represented the same wild genotype, quite significant variabilities (Cl((-)-R ) = 2.37-13.50 L/h and Cl((+)-S ) = 2.44-9.90 L/h) existed in the pharmacokinetics parameters of KTP. We concluded that KTP data obtained from healthy volunteers cannot be sufficient to predict disposition of KTP enantiomers in RA patients, especially when undergoing long-term multidrug therapy.

The study aimed to examine the effect of sunitinib on the plasma exposure of intravenous paracetamol and its major metabolite, paracetamol glucuronide. Both drugs share metabolic pathways in the liver, and the drug interactions between sunitinib and paracetamol administered in higher doses were reported. These interactions resulted in hepatotoxicity. The adult New Zealand male rabbits were divided into three groups (6 animals each): rabbits receiving sunitinib and paracetamol (SUN + PC), rabbits receiving sunitinib (SUN), and a control group receiving paracetamol (PC). Sunitinib was administered orally (25 mg) and paracetamol was administrated intravenously (35 mg/kg). Blood samples for sunitinib and SU12662 assays were collected up to 96 h after drug administration and for paracetamol and paracetamol glucuronide up to 300 min after drug administration. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin were analysed before and after drug administration. A number of pharmacokinetic parameters were analysed. There were no differences in the levels of AST, ALT, and bilirubin among the groups at either time point. Significantly higher values of AUC0-t , AUC0-∞ , and C max and lower clearance and volume of distribution of paracetamol were observed in group PC vs. group SUN + PC (p 0.01). The maximum plasma concentration of paracetamol glucuronide tended to be higher in group PC 213.27 μg/mL (90 % CI 1.06, 1.25; p = 0.0267). Statistically significant differences were revealed for paracetamol glucuronide mean residence time (MRT); MRT was higher in group SUN + PC than in group PC (p = 0.0375). The mean t max of paracetamol glucuronide was similar in both groups: SUN + PC and group PC (15 and 20 min, respectively). The mean t max of sunitinib was different in groups SUN + PC and SUN (10.0 and 7.0, respectively; p = 0.0134). At the studied doses, neither of the drugs, whether administered alone or together, had hepatotoxic effects. The present study was not able to confirm that sunitinib, administered at low doses in conjunction with paracetamol, displays a hepatoprotective effect. Significant differences were observed in some pharmacokinetic parameters of paracetamol.

Danirixin (GSK1325756) is a small, high-affinity, selective and reversible CXCR2 antagonist in development for treatment of chronic obstructive pulmonary disease. The objective of the study was to evaluate the relative bioavailability, including the inter-subject variability, of a conventional immediate-release (IR) formulation and two prototype bioenhanced formulations of danirixin during gastric acid suppression in a healthy, elderly population. A single-centre, crossover study in healthy male and female volunteers aged 65–80 years was conducted. Subjects were randomised to receive danirixin 50 mg IR in the fed and fasted states and danirixin 50 mg Bioenhanced Formulation 1 and 2 in the fasted state. All subjects also received omeprazole 20 mg each morning beginning 4 days prior to the first treatment period and continuing through danirixin dosing in the final treatment period. Twenty subjects were randomised and completed the study. Bioenhanced Formulation 2 in the fasted state demonstrated the highest adjusted geometric means for AUC(0–t), AUC(0–inf), AUC(0–24) and Cmax. Danirixin IR demonstrated adjusted means that were higher in the fed state compared with the fasted state. For all formulations tested, there was substantial inter-subject variability (CVb >100 % for all formulations). The overall incidences of adverse events (AEs) were 10 % for danirixin IR (both in the fed and fasted states) and 15–20 % for the bioenhanced formulations. The majority of AEs were mild in intensity. There were no serious AEs. Concomitant use of omeprazole resulted in large inter-subject variability in the exposure to danirixin. Bioenhanced formulation strategies could not overcome the effect of omeprazole on exposure and variability between subjects.

Radiolabelled [35S]-D-penicillamine was administered orally to DA-strain rats. After 72 hours approximately 65% of the dose was excreted with no significant differences between male and female animals. The major urinary product was inorganic sulphate with small amounts of D-penicillamine. Penicillamine disulphide, penicillamine-cysteine, S-methyl penicillamine and N-acetyl penicillamine were also found as metabolites. The female rat excreted significantly less sulphate (P less than 0.1) and more penicillamine disulphide (P less than 0.01) than the male. The residual radioactivity was found in the carcass, with slight concentration in the gut, skin, kidney, bladder and liver.

Micafungin is an echinocandin with potent activity against a broad range of fungal species, including Candida species. The pharmacokinetic and safety profiles of micafungin have been evaluated in individuals with mild-to-moderate hepatic dysfunction, but not in individuals with severe hepatic dysfunction. Therefore, the present study assessed the pharmacokinetics and safety of a single 100 mg dose of micafungin in healthy subjects (n = 8) and subjects with severe hepatic dysfunction (n = 8). Mean maximum plasma concentration of micafungin and mean area under the plasma micafungin concentration–time curve extrapolated to infinity were lower in subjects with severe hepatic dysfunction (7.3 ± 2.4 µg/mL and 100.1 ± 34.5 h·μg/mL, respectively) than in subjects with normal hepatic function (10.3 ± 2.5 µg/mL and 142.4 ± 28.9 h·μg/mL, respectively). Mean clearance was higher in subjects with severe hepatic dysfunction (1,098 ± 347 mL/h) than in subjects with normal hepatic function (728 ± 149 mL/h). Concentrations of albumin in subjects with severe hepatic dysfunction were lower. Assessments of micafungin plasma protein binding suggested that the higher clearance in subjects with severe hepatic dysfunction may be due to higher unbound concentrations. However, the magnitude of the differences was not considered clinically meaningful and is comparable with exposures reported elsewhere for a 100-mg dose in patients treated for invasive candidiasis. Thus, dose adjustment in subjects with severe hepatic dysfunction is not warranted. Micafungin was well tolerated in all subjects throughout the study.

The objectives of this qualitative review were to critically evaluate and summarize the currently available data on the use of anti-tuberculosis (TB) drugs during pregnancy, with a focus on treatment outcomes, safety, and pharmacokinetics. This qualitative, narrative review was based on literature searches in Medline, Pubmed, Embase, and Google Scholar (from their inception to 13 August 2020). Our search identified 22 papers related to treatment outcomes and 14 papers related to pharmacokinetic exposures and fetal distributions. While it is challenging to study this patient population, current evidence supports treatment of drug-susceptible TB, multidrug-resistant TB and latent TB infections. However, decisions regarding initiating, continuing, or discontinuing anti-tubercular medications while pregnant should be individualized and discussed with a specialist. Similarly, the pharmacokinetic data of anti-TB agents were mainly derived from small scale, observational studies many of which lacked high quality controls. Based on these data, it does not appear that pregnancy has an extensive impact on the pharmacokinetics of the majority of first-line and second-line agents, although caution (discussed in the review) should be exercised in data interpretation. Fetal drug exposure can also be significant and should be considered when selecting an anti-TB agent for longer term treatment. Overall, it is generally difficult to predict pregnancy-associated pharmacokinetic changes based only on drug’s physiochemical characteristics.

This paper aims to investigate the portal-vein absorption kinetics of berberine in rat, and the influence of P-gp inhibitors such as verapamil and borneol, to its absorption ability. In the paper, a validated UHPLC method was established to determine the berberine in plasma, and the portal-vein absorption model was applied to conduct the pharmacokinetic study. Animals were divided into four groups as follow: group berberine group (BG); group verapamil + berberine group (VBG); group borneol + berberine group (BBG) and group long-term use of borneol + berberine group (LBBG). Plasma samples were obtained at regular time intervals after administration and separated on Agilent 1290 Infinity UHPLC instrument. The method showed good linearity (r = 0.9988) over wide dynamic ranges (4.08–163.20 ng/mL). Variations within- and between-batch never exceeded 7.58 and 2.21 %, respectively. The extraction recovery rates ranged from 85.34 to 111.62 %. We discovered that the AUC of four group exhibited no significant differences (P > 0.05), and co-administration of berberine with borneol of group BBG and group LBBG in advance could both reduce the T max and C max as compared to group BG (P

Background and Objective: In the absence of characterization on pharmacokinetics and reference concentrations for hydroxychloroquine in COVID-19 patients, the dose and treatment duration for hydrochloroquine are currently empirical, mainly based on in vitro data, and may vary across national guidelines and clinical study protocols. The aim of this paper is to describe the pharmacokinetics of hydroxychloroquine in COVID-19 patients, considered to be a key step toward its dosing optimization. Methods: We have developed a population pharmacokinetic model for hydroxychloroquine in COVID-19 patients using prospectively collected pharmacokinetic data from patients either enrolled in a clinical trial or treated with hydroxychloroquine as part of standard of care in two tertiary Belgian hospitals. Results: The final population pharmacokinetic model was a one-compartment model with first-order absorption and elimination. The estimated parameter values were 9.3/h, 860.8 L, and 15.7 L/h for the absorption rate constant, the central compartment volume, and the clearance, respectively. The bioavailability factor was fixed to 0.74 based on previously published models. Model validations by bootstraps, prediction corrected visual predictive checks, and normalized prediction distribution errors gave satisfactory results. Simulations were performed to compare the exposure obtained with alternative dosing regimens. Conclusion: The developed models provide useful insight for the dosing optimization of hydroxychloroquine in COVID-19 patients. The present results should be used in conjunction with exposure-efficacy and exposure-safety data to inform optimal dosing of hydroxychloroquine in COVID-19., SCOPUS: ar.j, info:eu-repo/semantics/published

Background and Objective: p75ECD-Fc is a novel antagonist of toxic amyloid beta protein and other neurodegenerative factors with potential for the treatment of Alzheimer’s disease (AD). Preclinical studies showed that it can alleviate the AD pathologies in animal models of dementia. In a previous paper, we used non-compartmental pharmacokinetic analysis to obtain preliminary pharmacokinetic data for p75ECD-Fc in Sprague Dawley (SD) rats. We also studied the tissue distribution in terms of drug metabolism that helped us to understand possible mechanisms of action. Here, we aim to develop population pharmacokinetic models that can describe the pharmacokinetics of p75ECD-Fc in serum and tissues. Methods: p75ECD-Fc was delivered to SD rats via two routes (intravenous and subcutaneous) at a single dose of 3 mg/kg (n = 15). Blood (n = 12) and tissue samples (n = 10–15) were then separated at different time points for a total duration of 42 days post dosage. The concentration of p75ECD-Fc in serum and tissues was measured using an enzyme-linked immunosorbent assay. Results: Data were best fitted to a 2-compartment model with linear elimination kinetics. The population parameter estimates for clearance, and volume of central and peripheral compartments were 0.000176 L/h, 0.0145 L and 0.0263 L, respectively. The presence of anti-drug antibodies was added to the final model as a covariate on clearance. The subcutaneous bioavailability was estimated to be 53.5% with a first-order absorption rate constant of 0.00745 1/h. By modeling of individual tissue concentrations, p75ECD-Fc was found to exhibit modest tissue distribution with estimated tissue/plasma partition coefficients (R) ranging from 0.004 to 0.2. Conclusion: This is the first report of a pharmacokinetic model for p75ECD-Fc and these results may facilitate the ongoing development of p75ECD-Fc and translation to clinical studies. Refereed/Peer-reviewed

After more than six decades of its use as the mainstay antibiotic for the treatment of multidrug-resistant Gram-positive bacterial infections, dosing and monitoring of vancomycin therapy have not been optimized. The current vancomycin therapeutic guidelines recommend empiric doses of 15–20 mg/kg administered by intermittent infusion every 8–12 h in patients with normal kidney function. Additionally, the guidelines recommend trough concentration of 15–20 mg/L as a therapeutic goal for adult patients with severe infections. This review critically discusses the current guidelines considering the basic pharmacokinetics and pharmacodynamics of vancomycin and the recent published reports from clinical studies. More in-depth discussion will be focused on (1) providing evidence of advantages of administering vancomycin by continuous infusion compared to intermittent infusion; (2) revising the current practice of trough-only monitoring versus the area under concentration–time curve (AUC); and (3) assessing the current practice of weight-based dosing versus AUC-based dosing. Using the gathered information presented in this paper, two user-friendly and scientifically based dosing strategies are proposed to improve the efficiency of vancomycin dosing while avoiding the risk of nephrotoxicity and minimizing the cost of therapeutic drug monitoring.

Background and Objectives Cytochrome P450 2C9 (CYP2C9) is involved in the biotransformation of many commonly used drugs, and significant drug interactions have been reported for CYP2C9 substrates. Previously published physiologically based pharmacokinetic (PBPK) models of tolbutamide are based on an assumption that its metabolic clearance is exclusively through CYP2C9; however, many studies indicate that CYP2C9 metabolism is only responsible for 80–90% of the total clearance. Therefore, these models are not useful for predicting the magnitude of CYP2C9 drug–drug interactions (DDIs). This paper describes the development and verification of SimCYP®-based PBPK models that accurately describe the human pharmacokinetics of tolbutamide when dosed alone or in combination with the CYP2C9 inhibitors sulfaphenazole and tasisulam. Methods A PBPK model was optimized in SimCYP® for tolbutamide as a CYP2C9 substrate, based on published in vitro and clinical data. This model was verified to replicate the magnitude of DDI reported with sulfaphenazole and was further applied to simulate the DDI with tasisulam, a small molecule investigated for the treatment of cancer. A clinical study (CT registration # NCT01185548) was conducted in patients with cancer to assess the pharmacokinetic interaction of tasisulum with tolbutamide. A PBPK model was built for tasisulam, and the clinical study design was replicated using the optimized tolbutamide model. Results The optimized tolbutamide model accurately predicted the magnitude of tolbutamide AUC increase (5.3–6.2-fold) reported for sulfaphenazole. Furthermore, the PBPK simulations in a healthy volunteer population adequately predicted the increase in plasma exposure of tolbutamide in patients with cancer (predicted AUC ratio = 4.7–5.4; measured mean AUC ratio = 5.7). Conclusions This optimized tolbutamide PBPK model was verified with two strong CYP2C9 inhibitors and can be applied to the prediction of CYP2C9 interactions for novel inhibitors. Furthermore, this work highlights the utility of mechanistic models in navigating the challenges in conducting clinical pharmacology studies in cancer patients.

Pharmacokinetic (PK) interactions between the cytochrome P450 3A4 (CYP3A4) pathway and transdermally administered ethinyl estradiol (EE) and gestodene (GSD) were investigated. This paper reports the findings of three open-label, intra-individual, one-way crossover, Phase I trials. In two studies, women used a novel contraceptive patch for 3 weeks during two 4-week study periods; in the second period, the CYP3A4 inhibitors erythromycin (Study 1) or ketoconazole (Study 2) were administered concurrently. In a third study, women received single doses of the CYP3A4 model substrate midazolam, alone and after 3 weeks of concurrent patch application. In each period, the EE/GSD patch (delivering low EE and GSD doses resulting in the same systemic exposure as a combined oral contraceptive containing 0.02 mg EE and 0.06 mg GSD) was applied once weekly for 3 weeks, with one patch-free week. Erythromycin, ketoconazole, and midazolam were administered orally. Main outcome measures were area under the curves (AUCs) and maximum plasma concentration (C max) of EE, and total and unbound GSD (Studies 1 and 2). AUC and C max of midazolam (Study 3). Co-administration of CYP3A4 inhibitors did not affect EE metabolism, and had only weak effects on the PK of total and unbound GSD. The patch had no clinically relevant effect on metabolism of the CYP3A4 substrate midazolam.

The compound series of traditional anticholinergics [atropine (Atr), anisodamine (Ani), anisodine (AT3), and scopolamine (Sco)], naturally occurring belladonna alkaloid, have been approved for numerous therapeutic uses since 1970s. Tiotropium, a novel M receptor antagonist for the treatment of chronic obstructive pulmonary disease, was structurally modified based on atropine-like drugs. Clinical phenomena suggested that the changes of substituent group were related to the pharmacokinetic and pharmacodynamic characteristics of the agents. In an attempt to compare the pharmacokinetics of the series of anticholinergics and investigate the subsets motivating selective anticholinergic potencies, a sensitive LC–MS/MS method was established to analyze the differences of pharmacokinetic parameters. In this paper, we determined the pharmacokinetics of atropine, anisodamine, anisodine, scopolamine, and tiotropium after i.v. and i.g. single dose administration. After i.v. administration, the maximum drug plasma concentrations (C max) of Atr, Ani, AT3, and Sco were 274.25 ± 53.66, 267.50 ± 33.16, 340.50 ± 44.52, and 483.75 ± 78.13 ng/mL. Tiotropium had a slightly higher area under the curve with a significant increase of C max value. Because of their partial solubility, Atr, Ani, AT3, and Sco had different bioavailability in rats of 21.62, 10.78, 80.45 and 2.52 %, respectively. Following i.g. administration of tiotropium, the C max value below 20 ng/mL revealed the very low oral absorption. The urinary excretion rates of Atr, Ani, AT3, Sco and tiotropium were 11.33, 54.86, 32.67, 8.69 and 73.91 %. This work provided relatively comprehensive preclinical data on the series of anticholinergics, which may be used to explain the clinical adverse effects and applications.

Senkyunolide I is an active ingredient of Rhizoma Chuanxiong, a Chinese medicinal herb commonly used for the treatment of cardiovascular ailments. In the present paper, we describe the isolation and elucidation of senkyunolide I from the ethanol extract of Rhizoma Chuanxiong and its pharmacokinetic behavior after intravenous and oral administration to normal and migrainous rats. After intravenous administration, senkyunolide I was rapidly distributed (V z /F 2.07 ± 0.43 L/kg) and eliminated from the plasma (CL z 2.56 ± 0.29 L/h/kg and t 1/2z 0.56 ± 0.13 h). After administration orally to normal rats at two dosages (20 and 72 mg/kg), the pharmacokinetic parameters of senkyunolide I were as follows: T max 0.25 ± 0.06 and 0.38 ± 0.11 h, C max 5,236.3 ± 802.8 and 22,071.9 ± 3,456.1 mg/L, Area under the curve(AUC)(0−t) 5,217.5 ± 1,029.5 and 21,480.2 ± 3,003.1 μg h/L, respectively. Its oral absolute bioavailability at the two dosages was 67.2 and 76.9%, respectively. Intriguingly, migraine caused some significant changes in its pharmacokinetic parameter. For example, when compared with its pharmacokinetic behavior in normal rats at the two dosages, on average, its clearance decreased by 68% and volume of distribution increased by 342% in migrainous rats, both of which contributed to its several-fold increase in t 1/2z and AUC. C max and AUC of senkyunolide I increased almost proportionally with dose between 20 and 72 mg/kg and the pharmacokinetics fit linear kinetic feature. The pharmacokinetic parameters of senkyunolide I were significantly different in normal and migrainous rats, which should be taken into account during the design of a clinical dosage regimen for senkyunolide I.

With the purpose of describing the MAb ior-R3's kinetic behavior in disease state, this paper is focused on the study of this response using a human cancer (lung carcinoma cell line, H125) bearing nude mice animal model. This MAb was administered by a single 16 mg/Kg intravenous bolus dose and the blood samples were collected at several times ranging from 0 to 72 hours for serum drug quantification. The experimental data set was best fitted using a classical two-compartment mammilary pharmacokinetic (PK) model and the corresponding PK parameters were determined. Comparatively, the analysis of the more relevant physiologically-based PK parameters showed a significant enhancing of clearance as compound with the earlier reported study on healthy mice, increasing from 0.09 to 0.19 mL/h (p

Veterinary medicine plays a significant role in the development of animal husbandry. Drugs residual in food would follow the food-chain coming into human body, which might bring hidden dangers to people. Chicken is the prime source of meat food, whose quality is important for our life and health. Therefore, it is necessary to realize the withdrawal period and establish an efficient, sensitive and accurate method for monitoring the metabolic process of drugs in chicken body. In this paper, the pharmacokinetics of aminophylline in partridge chicken after intravenous and oral administration was investigated using a sensitive high-performance liquid chromatography method. Plasma concentration-time profiles of aminophylline were analyzed by a non-compartmental model using Topfit 2.0. Following intravenous and oral administration, the peak concentrations (C max) were found to be (16.5 ± 3.0) µg/mL at (0.08 ± 0) h and (7.4 ± 1.5) µg/mL at (1.83 ± 1.11) h, respectively. The elimination half-time (t 1/2) after intravenous and oral administration were, respectively, (13.1 ± 4.17) h and (11.65 ± 1.14) h. Areas under the plasma concentration-time curve (AUC) were (209.6 ± 22.8) µg h mL(-1)(AUC0-t ) and (219.5 ± 28.3) µg h mL(-1) (AUC0→∞ ) after intravenous, and (165.1 ± 37.0) µg h mL(-1)(AUC0-t ) and (179.3 ± 35.6) µg h mL(-1) (AUC0→∞ ) after oral administration. Mean retention time (MRT) after intravenous and oral administration were, respectively, (14.06 ± 0.86) and (15.27 ± 0.62) h. The total clearance rates (CLtol) were (0.77 ± 0.10) mL min(-1) kg(-1) of intravenous and (0.97 ± 0.20) mL min(-1) kg(-1) of oral administration. The apparent distribution volume (V d) was (0.87 ± 0.27) and (0.97 ± 0.20) L kg(-1), respectively, for intravenous and oral administration. The absolute bioavailability (F) after oral administration was (83.1 ± 11.7) %. The results showed that aminophylline in partridge chickens had a longer elimination half-time, a smaller clearance rate, as well as a higher absolute bioavailability for oral administration. Therefore, aminophylline in partridge chickens produced a long healing efficacy and oral administration can achieve a good absorption which could meet the requirement.

This paper deals with press-coated modified release tablets in which the drug dose is situated in the core or is divided between the core and the coat. The coat contains polymer (sodium alginate or hydroxypropylmethyl cellulose, HPMC) to control drug release. The main objective was to investigate how the pharmacokinetic profile of the model drug could be modified by altering the proportion of the drug between the core and the coat. The effect of the amount of the polymer in the coat was also studied. Bioavailability tests were carried out on healthy volunteers. In the absorption curves of the tablets containing 50%, 67% and 80% of the drug in the core and 180 mg HPMC in the coat a bimodal profile was observed. No bimodal release pattern in the in vitro dissolution studies was found. If the whole dose was incorporated in the core the absorption curve has only one clear t(max) value at about 10 h. Doubling the amount of HPMC in the coat dramatically decreased drug absorption. It was concluded that, if a slightly reduced t(max)-value was required, the viscosity grade of HPMC used should be lowered.

In the present paper, a nonlinear compartmental model for theophylline pharmacokinetics is developed. The analytical solution of the model, in parametric form, is derived under plateau conditions for plasma metabolite concentration. The parameters are obtained from plasma and urine data using best fitting techniques and their values are used in order to calculate maintenance intravenous infusion. Numerical simulation is then performed in order to compare the drug concentration obtained by our approach with that of alternative intravenous regimens. The differences argue for individualized dosage regimens, since theophylline is a drug with a narrow therapeutic window, and its concentration at the active sites strongly depends on characteristic parameters of the patient’s response. Our results show that it is possible to estimate the patients’ parameters during the first 8 h after intravenous administration of the drug and these parameters can be used to design an individualized dosage regimen in patients receiving theophylline intravenously.

A generic drug product (test product) is bioequivalent to an innovator product (reference product) when their bioavailabilities in the same molar dose are similar. Bioavailability is expressed by pharmacokinetic parameters such as the area under plasma concentration-time curve (AUC), the maximum plasma concentration (Cmax) and the time of maximum plasma concentration (tmax). The assessment of bioequivalence is carried out by in vivo bioequivalence studies. This paper examines and appraises design issues for performing a bioequivalence study: the use of crossover, parallel, replicated, and add-on designs; and the determination of sample size. In addition, it presents the valid statistical approaches for proving bioequivalence: average bioequivalence on transformed and untransformed data; parametric and non-parametric analyses; moment based individual bioequivalence; direct curve comparison metrics.

There have been reports wherein the total clearance of certain drugs exceeded the blood flow rate when blood concentration data following an intravenous injection was used. It is theoretically unusual that for drugs carried to the tissue by blood, the quantity eliminated is larger than the quantity carried. Nevertheless, the problem about total clearance still needs to be solved. The present paper proposes an equation to ensure that such unusual values do not arise.

Bioavailability and bioequivalence evaluations of drug products carried out using the experimental maximum concentration (Cmax) and the experimental time to reach Cmax (Tmax), are not advisable for slow-release formulations and for trials performed with saliva as biologic fluid. When slow-release curves are considered the drug concentration profiles usually show multiple peaks, making it difficult to compute a Cmax,Tmax value. The saliva profile throughout time shows a high variability observed as more than one peak in the saliva concentration versus time curves. In both cases, even if there is a major peak, when the statistical analysis of the data is performed, an important variability in Cmax results in high values in the residual variance of the ANOVA test. Consequently, the power of the bioequivalence test decreases and sometimes it is not possible to conclude on bioequivalence. The average concentration (Cav), the average maximum concentration (Cmax,av) and Cmax,av/Cav x 100 (%Cmax,av) are proposed in this paper as possible parameters in order to evaluate the profile of the concentration-time curves, as they reduce the residual variability in bioequivalence studies.

There is current emphasis for extended integration of pharmacokinetics (PK) and pharmacodynamics (PD) into all phases of new drug development, including large-scale clinical trials. In this paper, we focus on study design and data analysis issues for the investigation of pharmacokinetic/pharmacodynamic and blood level/effect relationships in patients. The application of descriptive and model-based regression statistical methodology for including sparse drug systemic concentration data in the analysis of efficacy and safety is illustrated by examples chosen from diverse therapeutic areas. The population approach, based on mixed-effects modelling, is one such methodology, which also provides new tools for analysis of response vs dose and response vs time data. The existence of a variety of statistical techniques for handling complex PK/PD time-varying data should increase the impact of such data analysis on future drug development.

A multitude of in vivo variables can influence systemic drug absorption after intake of an oral formulation. For the measurement of consistent in vivo parameters within and between pharmacokinetic studies it is of primary importance that such variables be recognized. Consequently, as many variables as possible should be eliminated or controlled by proper study designs to prevent (or minimize) their disturbance of in vitro/in vivo correlations. The possible influences of some important variables are elaborated and discussed in this paper. The influences of food can be anticipated and controlled against the background of gastrointestinal physiology with and without food and its interplay with the dosage form. Food, and also posture and exercise, may influence splanchnic-hepatic blood flow which may substantially affect the absorption of drugs with a high first-pass metabolism. The influence of the discussed variables may be modified by the dosage form of a particular drug. Single dose studies are appropriate for studying immediate release formulations and in the development of controlled release formulations. Multiple dose studies are preferred for the formal validation of controlled release formulations.

The role of N4-acetylsulfadimethoxine (N4-AcSDM), a major metabolite of sulfadimethoxine (SDM), in protein binding and pharmacokinetic interactions between SDM and bucolome (BCP) was investigated in rabbits. When SDM and BCP were intravenously co-administered, BCP indirectly reduced the serum protein binding of SDM by causing a marked increase of N4-AcSDM concentration in serum, and significantly increased the steady-state volume of distribution (Vss) and total body clearance (C1tot) of SDM. In addition, the co-administration of N4-AcSDM was found to increase Vss and C1tot of SDM. These results lead us to conclude that N4-AcSDM plays an important role in protein binding and pharmacokinetic interactions between SDM and BCP in rabbits. Several investigations have demonstrated that a metabolite plays an important role in drug-drug interaction. For example, Sellers et al. (1) reported that when warfarin and chloral hydrate are co-administered, a major metabolite of chloral hydrate, trichloroacetic acid, reduces the plasma protein binding of warfarin and enhances its anti-coagulant activity. Our previous paper (2) showed that probenecid indirectly reduces the plasma protein binding of sulfadimethoxine (SDM) by causing a marked increase in the plasma concentration of N4-acetylsulfadimethoxine (N4-AcSDM), which is a major metabolite of SDM (3) and strongly displaces SDM from its plasma protein binding sites (2). However, as yet the role of this metabolite in drug-drug interaction has not been fully examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Background and Objectives Previous pharmacokinetic studies of the inhaled corticosteroid, fluticasone furoate (FF), and the long-acting, beta2-receptor agonist, vilanterol (VI) have been performed in relatively small populations using non-compartmental pharmacokinetic methods and censored data (due to low drug exposure relative to assay sensitivity). This paper presents a population pharmacokinetic analysis, utilizing pooled concentration–time data from clinical studies in healthy subjects and from global trials in patients with chronic obstructive pulmonary disease (COPD). The objective of this analysis was to characterize the population pharmacokinetics of FF and VI following once-daily inhalation dosing of FF/VI or the individual components (FF and VI) and to identify significant covariates that impact systemic exposure to FF and VI in this population. Methods Population pharmacokinetic methods that maximize the likelihood of all data were developed to describe systemic exposure to FF and VI following once-daily FF/VI, FF, or VI, and to identify significant covariates that impact the pharmacokinetics. COPD patients (N = 1225 for the FF analysis and N = 1091 for the VI analysis; 94 and 93 % of total data, respectively) and healthy subjects contributed to the analysis. Results FF data were described by a two-compartment model with first-order absorption and elimination. The population grouping “race” was a significant covariate on inhaled clearance (CL/F). The area under the curve over 24 h (AUC0–24) for FF was higher for East Asian, Japanese, and South East Asian (average 23–30 %) and Asian Central, White Arabic, American Indian/Native Alaskan, and ‘other’ (10–26 %) subjects compared with White/Caucasians. VI pharmacokinetics were described by a three-compartment model with zero-order absorption and first-order elimination. Significant demographic covariates identified to affect pharmacokinetics of VI were age [on CL/F and central volume (V 1/F)], bodyweight (on CL/F), sex and smoking (on V 1/F). Conclusions While significant effects of the covariates were observed in this study, the magnitude of these effects on systemic exposure is not large enough to warrant FF/VI dosage adjustment in patients with COPD. Electronic supplementary material The online version of this article (doi:10.1007/s13318-015-0303-4) contains supplementary material, which is available to authorized users.