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Background: Dimethyl fumarate is used to treat patients with relapsing-remitting multiple sclerosis. After ingestion, it is rapidly hydrolyzed to the active primary metabolite monomethyl fumarate., Objective: The main objective of our study was to analyze serum concentrations of monomethyl fumarate during routine health care in patients with multiple sclerosis treated with a fixed dose of dimethyl fumarate., Methods: In the pilot cross-sectional study, data from 42 patients treated with dimethyl fumarate at a dose of 240 mg twice daily were collected. Concentrations of the active metabolite monomethyl fumarate were determined at 1-8 h (median, 3 h) or 10-14 h (median, 13 h) after taking the dose. The relationship between monomethyl fumarate concentrations and absolute lymphocyte count was evaluated., Results: Concentrations of monomethyl fumarate ranged from 2.5-3177.9 μg/L, with most concentrations being undetectable approximately 10 hours after administration. In the 1-8 h (median, 3 h) post-dose subgroup, the concentration/dose ratio ranged widely from 0.04-6.62. The median concentration of monomethyl fumarate in the group with the absolute lymphocyte count <0.8 x 10^9/l was more than four times higher than in the group with the absolute lymphocyte count ≥0.8 x 10^9/l (median 440.1 μg/L versus 98.4 μg/L)., Conclusion: The wide interindividual variability in monomethyl fumarate pharmacokinetics could contribute to the differential response to dimethyl fumarate in multiple sclerosis patients. A nonsignificant but noticeable trend was observed in the relationship of higher serum monomethyl fumarate concentrations to absolute lymphocyte counts., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

ST segment elevation myocardial infarction (STEMI) is one of the most common global causes of cardiovascular disease-related death. Several metabolites may change during STEMI. Hence, analysis of metabolites in body fluid may be considered as a rapid and accurate test for initial diagnosis. This study has therefore attempted to determine the variation in metabolites identified in the serum of STEMI patients (n = 20) and 15 controls. Samples collected from the Cardiology Department, Medical Faculty, Ataturk University, were extracted by liquid-liquid extraction and analysed using liquid chromatography quadrupole time-of-flight mass spectrometry. The METLIN database was used for the identification and characterization of metabolites. According to Q-TOF/MS measurements, 231 m/z values, which were significantly different between groups (P < 0.01 and fold analysis >1.5) were detected. Metabolite identification was achieved via the Human Metabolome database. According to the multivariate data analysis, leucine, isoleucine, l-proline, l-alanine, glycine, fumaric acid, citrate, succinate and carnitine levels were decreased, whereas levels of propionic acid, maleic acid, butyric acid, urea, oleic acid, palmitic acid, lysoPC [18:2(9Z)], glycerol, phoshpatidylethanolamine, caffeine and l-lactic acid were increased in STEMI patients compared with controls. In conclusion, malonic acid, maleic acid, fumaric acid and palmitic acid can be used as biomarkers for early risk stratification of patients with STEMI., (© 2019 John Wiley & Sons, Ltd.)

Chronic kidney disease (CKD) involves significant metabolic abnormalities and has a high mortality rate. Because the levels of serum metabolites in patients with CKD might provide insight into subclinical disease states and risk for future mortality, we determined which serum metabolites reproducibly associate with mortality in CKD using a discovery and replication design. Metabolite levels were quantified via untargeted liquid chromatography and mass spectroscopy from serum samples of 299 patients with CKD in the Modification of Diet in Renal Disease (MDRD) study as a discovery cohort. Six among 622 metabolites were significantly associated with mortality over a median follow-up of 17 years after adjustment for demographic and clinical covariates, including urine protein and measured glomerular filtration rate. We then replicated associations with mortality in 963 patients with CKD from the African American Study of Kidney Disease and Hypertension (AASK) cohort over a median follow-up of ten years. Three of the six metabolites identified in the MDRD cohort replicated in the AASK cohort: fumarate, allantoin, and ribonate, belonging to energy, nucleotide, and carbohydrate pathways, respectively. Point estimates were similar in both studies and in meta-analysis (adjusted hazard ratios 1.63, 1.59, and 1.61, respectively, per doubling of the metabolite). Thus, selected serum metabolites were reproducibly associated with long-term mortality in CKD beyond markers of kidney function in two well characterized cohorts, providing targets for investigation., (Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Dimethyl fumarate (DMF) is the methyl ester of fumaric acid, after oral administration completely converts to its active metabolite monomethyl fumarate (MMF). A simple, rapid and sensitive LC-MS/MS method was developed and validated for the quantification of MMF in human plasma. Monomethyl fumarate d3 was used as an internal standard (IS). The analyte and the IS were extracted from plasma using a selective solid phase extraction technique. The clean samples were chromatographed on a C 18 column using formic acid and acetonitrile (25:75, v/v) as mobile phase. An API-4000 LC-MS/MS system equipped with turbo ion spray (TIS) source and operated in multiple reactions monitoring (MRM) mode was used for the study. The method was validated for linearity in the range of 5.03-2006.92ng/mL. Also, a number of stability tests were conducted to evaluate the stability of analyte, IS in plasma samples and in neat samples, the results comply with recent bioanalytical guidelines. A shortest run time helped us to analyze more than 300 samples in a day. The method was applied to a pharmacokinetic study in ten healthy male Indian subjects and the study data was authenticated by conducting incurred sample reanalysis (ISR)., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel orotic acid salt form of tenofovir disoproxil (DA-2802) was developed and is expected to replace the fumaric acid salt form. The pharmacokinetic (PK) characteristics and tolerability profiles of DA-2802 were compared to those of tenofovir disoproxil fumarate (TDF, Viread ® ) in healthy subjects. A randomized, open-label, single-dose study was conducted in 36 healthy subjects using a two-treatment, two-period, and two-sequence crossover design. Subjects received a single oral dose of 319 mg DA-2802 or 300 mg TDF, during each period, with a 7-day washout. Serial blood samples were collected pre-dosing and up to 72 hours post-dosing in each period, for determination of serum tenofovir concentration, which was measured by ultra-performance liquid chromatography-tandem mass spectrometry. A non-compartmental method was used to obtain PK parameters of tenofovir. For comparison between the two tenofovir disoproxil salts, the 90% confidence intervals (90% CIs) of geometric mean ratios of DA-2802 to TDF for the maximum concentration (C max ) and the area under the concentration-time curve to the last quantifiable concentration (AUC 0-t ) were determined. The tolerability profiles of tenofovir were assessed by evaluation of adverse events and vital signs, physical examination, ECG, and clinical laboratory tests. The serum tenofovir concentration-time profiles of DA-2802 or TDF were comparable in 32 subjects who completed the study. In both profiles, a two-compartmental elimination with first-order elimination kinetics in the terminal phase was reported in a few subjects, showing a secondary peak in the initial phase of elimination. The geometric mean ratio (90% CI) of DA-2802 to TDF was 0.898 (0.815-0.990) for C max and 0.904 (0.836-0.978) for AUC 0-t . There were no clinically significant findings in the tolerability assessments. DA-2802 showed comparable PK characteristics and tolerability profiles to TDF., Competing Interests: Disclosure Ms Mun Ju Choi and Mr Tae Young Oh are employees of Dong-A ST Co., Ltd. None of the authors of this study are involved in financial or personal relationships with agencies, institutions, or organizations that could inappropriately influence the statistical analysis plan or interpretation of this work. The authors report no other conflicts of interest in this work.

Citrin deficiency causes adult-onset type II citrullinemia (CTLN-2), which later manifests as severe liver steatosis and life-threatening encephalopathy. Long-standing energy deficit of the liver and brain may predispose ones to CTLN-2. Here, we compared the energy-driving tricarboxylic acid (TCA) cycle and fatty acid β-oxidation cycle between 22 citrin-deficient children (age, 3-13years) with normal liver functions and 37 healthy controls (age, 5-13years). TCA cycle analysis showed that basal plasma citrate and α-ketoglutarate levels were significantly higher in the affected than the control group (p<0.01). Conversely, basal plasma fumarate and malate levels were significantly lower than those for the control (p<0.001). The plasma level of 3-OH-butyrate derived from fatty acid β-oxidation was significantly higher in the affected group (p<0.01). Ten patients underwent sodium pyruvate therapy. However, this therapy did not correct or attenuate such deviations in both cycles. Sodium pyruvate therapy significantly increased fasting insulin secretion (p<0.01); the fasting sugar level remained unchanged. Our results suggest that citrin-deficient children show considerable deviations of TCA cycle metabolite profiles that are resistant to sodium pyruvate treatment. Thus, long-standing and considerable TCA cycle dysfunction might be a pivotal metabolic background of CTLN-2 development., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Cobalamin C disease (cblC), which leads to methylmalonic acidemia with homocystinuria, is the most common inherited disorder of vitamin B12 metabolism. Reported ocular findings associated with cblC have been maculopathy, pigmentary retinopathy, and optic nerve atrophy. Cobalamin A disease (cblA) which causes an isolated methylmalonic acidemia without homocystinuria is rarer than cblC. This is the first detailed report of the ocular findings associated with cblA. We also describe the spectrum of ocular findings in our cblC patients., Materials and Methods: A case series describing the ophthalmologic clinical course of six patients with a diagnosis of cobalamin C type and one patient with cobalamin A type of methylmalonic acidemia. Patients were diagnosed through biochemical laboratory testing and genetic analysis was conducted on most patients. Longitudinal fundus findings, optical coherence tomography (OCT), autofluorescence, and electrophysiology were followed in the patients., Results: The cblA patient demonstrated a relatively mild ocular phenotype with late-onset and slowly progressing temporal disc pallor and peripapillary atrophy in the second decade of life. The patient maintained good visual acuity and central vision, without evidence of maculopathy. The six cblC patients demonstrated a range of ocular findings from unremarkable and mild phenotypes to significant retinopathy, including bull's eye maculopathy, severe maculopathy with punched out chorioretinal atrophy, peripheral bone spicules, and optic nerve atrophy., Conclusions: The spectrum of ocular manifestations seen with inherited disorders of cobalamin metabolism is wide, ranging from mild optic nerve atrophy to severe macular or retinal degeneration. This heterogeneity may in part reflect the associated biochemical phenotype, such as that observed between our cblA and cblC patients. We also observed heterogeneity within the cblC type in agreement with previous reports.

Background: Fumaric acid is a commonly used excipient in pharmaceutical products. It is not known if its presence may lead to fluctuation of endogenous fumarate levels. An LC-MS/MS method was developed and validated to quantify fumarate in support of a toxicokinetics study., Results: Stability evaluation showed that endogenous fumarate was stable for 6 h at room temperature, while exogenously added fumaric acid was converted to malate within 1 h due to the presence of fumarase. Citric acid, a fumarase inhibitor, prevented the conversion of added fumaric acid in rat plasma., Conclusion: The method was validated in citric acid stabilized rat plasma using a surrogate matrix approach. A discrepancy in stability was observed between endogenous fumarate and exogenously added fumaric acid.

A sensitive UPLC-MS/MS method was developed and validated for simultaneous estimation of aliskiren hemifumarate (ALS), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) in spiked human plasma using valsartan as an internal standard (IS). Liquid-liquid extraction was used for purification and pre-concentration of analytes. The mobile phase consisted of 0.1% formic acid in ammonium acetate buffer (0.02 M, pH 3.5) and methanol (25:75, v/v), flowing through XBridge BEH (50 × 2.1 mm ID, 5 µm) C18 column, at a flow rate of 0.6 mL min(-1). Multiple reaction monitoring (MRM) transitions were measured using an electrospray source in the positive ion mode for ALS and AML, whereas HCZ and IS were measured in negative ion mode. Validation of the method was performed as per US-FDA guidelines with linearity in the range of 2.0-400.0, 0.3-25.0 and 5.0-400.0 ng mL(-1) for ALS, AML and HCZ, respectively. In human plasma, ALS, AML and HCZ were stable for at least 1 month at -70 ± 5°C and for at least 6 h at ambient temperature. After extraction from plasma, the reconstituted samples of ALS, AML and HCZ were stable in the autosampler at ambient temperature for 6 h. The LC-MS/MS method is suitable for bioequivalence and pharmacokinetic studies of this combination., (© The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

A simple, unique and selective HPLC-PDA method was developed and validated for the simultaneous estimation of aliskiren (ALS) and amlodipine (AML) in human plasma. Extraction of the sample was accomplished by protein precipitation. Plasma proteins were precipitated by employing acetonitrile containing hydrochlorothiazide as internal standard. The compounds were analyzed by HPLC by using PDA detector on a Hibar C18 (250 × 4.6 mm) column with a mobile phase comprising acetonitrile and phosphate buffer (pH 4.2 and 25 mm; 60:40 v/v) with a flow rate of 0.8 mL/min. Different sample pretreatment techniques were evaluated but protein precipitation was found to be satisfactory, offering good recovery values of 97.11-98.45% for ALS and 97.5-99.12% for AML. The within-day precisions for ALS were 96.66, 99.16 and 99.41% at 90, 240 and 480 ng/mL, respectively, and for AML they were 97.27, 99.54 and 99.31% at 3.3, 8.8 and 17.6 ng/mL, respectively. The between-day precisions for ALS were 96.66, 99.16 and 99.41% at 90, 240 and 480 ng/mL, respectively and the between-day precisions for AML were 98.18, 99.20 and 99.40% at 3.3, 8.8 and 17.6 ng/mL, respectively. The limit of quantitation was 30 and 1.0 ng/mL for ALS and AML respectively. Different constituents of plasma proteins did not interfere with the absolute recovery of ALS and AML., (Copyright © 2014 John Wiley & Sons, Ltd.)

Given the increasing popularity of aliskiren, particularly in combination with angiotensin converting enzyme inhibitor (e.g. enalapril), it is important to determine whether its use in combination with these agents is associated with potentially life threatening safety events. Analytical methods for the simultaneous determination of both drugs in plasma and urine utilized in clinical studies on efficacy and safety have not been fully described in the literature. In this work, a new, fast and reliable method using a digitally controlled microextraction by packed sorbent (eVol(®)-MEPS) followed by ultra-high performance liquid chromatography (UHPLC) coupled with tandem mass spectrometry (MS/MS) was developed and validated to quantify an aliskiren, enalapril and its active metabolite in both human plasma and urine. Chromatographic separation was accomplished on a Poroshell 120 EC-C18 column with a gradient elution system consisting of 0.1% formic acid in water and acetonitrile (1.5min of total analysis). Detection was performed by multiple reaction monitoring (MRM) mode using electrospray ionization in the positive ion mode. This assay method has been fully validated in terms of selectivity, linearity, accuracy, precision, stability, recovery and matrix effect. The developed method can be applied to the routine determination of selected compounds in human plasma and urine and can be useful to elucidate the mechanisms of the potential risks triggered by the combination of aliskiren and enalapril as well as its active metabolite enalaprilat., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A simple and sensitive HPLC method has been developed for the determination of aliskiren in human plasma through derivatization with 1-naphthyl isocyanate. The separation was achieved on a C18 column using a mobile phase consisting of acetonitrile/water/phosphoric acid (45:55:0.01, v/v/v, pH 3.2) in a flow rate of 1mL/min with UV detection at 230nm. Caffeine was used as an internal standard. The factors influencing the derivatization reaction yields were carefully studied and optimized. The method was linear over the concentration range of 5-400ng/mL with a detection limit of 0.5ng/mL and a limit of quantification of 1.0ng/mL. The relative standard deviation was less than 4.2% for both intra-day assay and inter-day assay results. No interferences from endogenous compounds were encountered. The percentage recovery was in the range 97.1-98.6%. The method is suitable for routine therapeutic drug monitoring and for pharmacokinetic studies., (Copyright © 2013 Elsevier B.V. All rights reserved.)

This paper describes a simple, rapid and sensitive liquid chromatography/tandem mass spectrometry assay for the determination of aliskiren in human plasma using nevirapine as an internal standard. Analyte and the internal standard were extracted from 100 μL of human plasma via liquid-liquid extraction using tert-butyl methyl ether. The chromatographic separation was achieved on a C18 column using a mixture of acetonitrile and 0.1% formic acid (90:10, v/v) as the mobile phase at a flow rate of 0.9 mL/min. The calibration curve obtained was linear (r(2) ≥ 0.99) over the concentration range of 0.10-1013 ng/mL. Method validation was performed as per US Food and Drug Administration guidelines and the results met the acceptance criteria. A run time of 2.2 min for each sample made it possible to analyze a greater number of samples in a short time, thus increasing the productivity. The proposed method was found to be applicable to clinical studies., (Copyright © 2013 John Wiley & Sons, Ltd.)

Dimethylfumarate (DMF), the essential ingredient of the drug product Fumaderm®, is used to treat psoriasis with a recognized favorable long-term safety profile. Interestingly, the mode of action and the pharmacokinetics of DMF in psoriasis or multiple sclerosis are not fully explored. It is known that DMF as an α,β-unsaturated carboxylic acid ester forms an adduct with the antioxidant glutathione in vitro via a Michael-type addition within a very short period of time. In addition, it was shown that this reaction also takes place in vivo since the mercapturic acid of DMF was detected in urine of psoriasis patients after oral intake of Fumaderm®. To verify the hypothesis that DMF reacts with GSH already in or even before entering the portal vein blood an in vivo study in rats was initiated and portal vein blood was analyzed for the presence of DMF, MMF, GS-DMS and break down products, after DMF was given directly into the small intestine. The results show that no free DMF could be detected in the rat portal vein blood at any time point. MMF was the dominant metabolite and GS-DMS was also detectable in portal vein blood. In the rat mucosa the glutathione adducts of DMF and MMF were present. The data obtained provide evidence that the modulation of immune-mediated inflammatory pathways responsible for development of psoriasis and MS are targeted by DMF regulating redox-sensitive pathways for which the reaction with glutathione by DMF plays a crucial role.

Objective: To assess the pharmacokinetics (PK) and safety profile of aliskiren in pediatric patients (6-17 years old) with hypertension., Methods: Patients were randomized to a single weight-based dose of either 2 mg/kg (n = 19) or 6 mg/kg (n = 20) of aliskiren daily for 8 days. The PK, pharmacodynamics, safety profile, and efficacy of aliskiren were assessed., Results: Of the 39 randomized patients, 37 (94.9%) completed the study. Aliskiren plasma concentration (maximum plasma concentration and area under the plasma concentration-time curve) increased dose dependently, achieving peak concentrations in 1 to 2 hours, and t(max) was comparable across the dose and age groups. Treatment-emergent adverse events (AEs) were reported in 18 (46.2%) patients, with headache, abdominal pain, and nausea being the most frequent., Conclusions: Aliskiren 2 mg/kg and 6 mg/kg daily showed dose-dependent increases in the plasma concentration. The drug was well tolerated in hypertensive children aged 6 to 17 years. AEs were generally mild and not related to either the drug or the dose.

Background and Objective: The antihypertensive effects of the direct renin inhibitor aliskiren last substantially longer after treatment withdrawal than expected based upon its plasma half-life. This may be attributable to drug accumulation in the kidney as recently shown in rats and mice. Since aliskiren binds to renin we examined in the present study whether this accumulation depends on the renin content of the kidney., Methods: For this we measured the aliskiren concentration in the kidney of wild-type as well as AT1a receptor(-/-) and Ren1c(-/-) mice. AT1a receptor(-/-) mice overexpress renin due to the lack of angiotensin II-mediated negative feedback, whereas Ren1c(-/-) mice lack renal renin expression., Results: Accumulation of aliskiren was found in the kidney of wild-type mice. However, renal accumulation was neither influenced by the overexpression nor by the absence of renin in the kidney. It was recently shown that the effects of aliskiren can be blocked by a handle region peptide, which inhibits the nonproteolytic activation of prorenin bound to the (pro)renin receptor. To investigate whether this putative (pro)renin receptor blocker influences renal aliskiren accumulation, we administered the blocker in addition to aliskiren. No influence on renal aliskiren accumulation was observed., Conclusion: These data confirm accumulation of aliskiren in the murine kidney and demonstrate that neither renin nor (pro)renin receptor-bound prorenin are major players in this process.

The orally active direct renin inhibitor aliskiren is approved for the treatment of essential hypertension in adults. Analytical methods utilized in clinical studies on efficacy and safety have not been fully described in the literature but need a large sample volume ranging from 200 to 700 μL, rendering them unsuitable particularly for pediatric applications. In the assay presented only 100 μL of serum is needed for mixed-mode solid-phase extraction. The chromatographic separation was performed on Xselect(TM) C18 CSH columns with mobile phase consisting of methanol-water-formic acid (75:25:0.005, v/v/v) and a flow rate of 0.4 mL/min. Running in positive electrospray ionization and multiple reaction monitoring the mass spectrometer was set to analyze precursor ion 552.2 m/z [M + H](+) to product ion 436.2 m/z during a total run time of 5 min. The method covers a linear calibration range of 0.146-1200 ng/mL. Intra-run and inter-run precisions were 0.4-7.2 and 0.6-12.9%. Mean recovery was at least 89%. Selectivity, accuracy and stability results comply with current European Medicines Agency and Food and Drug Administration guidelines. This successfully validated LC-MS/MS method with a wide linear calibration range requiring small serum amounts is suitable for pharmacokinetic investigations of aliskiren in pediatrics, adults and the elderly., (Copyright © 2012 John Wiley & Sons, Ltd.)

Aim: To evaluate the efficacy of nitrofurans in children and adolescents with pyelonephritis in the presence of crystalluria., Subjects and Methods: The study included 50 patients aged 4-14 years with chronic pyelonephritis in the presence of dysmetabolism. The patients underwent general blood test, general urinalysis with an urocytogram, bacteriological examination of urine, biochemical test of serum (uric acid, calcium, phosphorus, magnesium, urea, and creatinine) and 24-hour urinary excretion (uric acid, oxalates, calcium, phosphorus, and magnesium) at hospital admission and over time. The treatment regimen for Group 1 patients after antibiotic therapy involved furamag, Group 2 received furagin. The drugs were used in a dosage of 2 mg/kg/day in 2 divided doses for 14 days. Complaints, major clinical manifestations, crystalluria patterns, and a number of laboratory findings were analyzed over time., Results: The urinary sediment showed leukocyturia and bacteriuria in all the patients, oxaluria in 70% of the patients, uraturia in 10%, and mixed crystalluria in 20%. The main etiological agent of pyelonephritis was Escherichia coli (48.4%). Increased serum uric acid concentrations were revealed in 14% of the patients. Daily urine tests revealed hyperoxaluria, hyperuricosuria, and hypercalciuria in 86, 18, and 8% of the patients, respectively; urinary magnesium excretion was reduced in 86%. After treatment, Group 1 patients showed a more marked therapeutic effect in terms of a number of indicators (leukocyturia, crystalluria, uricosuria, magnesuria)., Conclusion: The results of the study showed that the antibacterial therapy involving antibiotics and nitrofurans for an exacerbation of chronic pyelonephritis in the presence of crystalluria not only provides an anti-inflammatory effect, but also leads to reductions in the level of crystalluria and the urinary content of uric acid and calcium. There was a significantly marked reduction in crystalluria, serum uric acid, and urinary oxalates and calcium in the children taking furamag. Out of nitrofurans, furamag may be recommended as the drug of choice to treat urinary tract infections in the presence of crystalluria.

Purpose: To conduct a mechanistic investigation of the interaction between aliskiren and grapefruit juice in healthy subjects., Methods: Twenty-eight subjects received an oral dose of aliskiren 300 mg (highest recommended clinical dose) with 300 mL of either water or grapefruit juice in a two-way crossover design. Safety and pharmacokinetic analyses were performed. In vitro studies were performed in HEK293 cells to investigate the role of organic anion transporting polypeptide (OATP) transporter-mediated uptake of aliskiren., Results: Co-administration of a single dose of aliskiren with grapefruit juice decreased the plasma concentration of aliskiren, with mean decreases in the AUC(inf), AUC(last), and C(max) of 38, 37, and 61%, respectively. The uptake of [¹⁴C]aliskiren into OATP2B1-expressing cells was essentially the same as that into control cells, and the inhibitor combination atorvastatin and rifamycin had no effect on [¹⁴C]aliskiren accumulation in either cell type. The uptake of [¹⁴C]aliskiren and [³H]fexofenadine was linear in OATP1A2-expressing cells and was reduced by naringin, with IC₅₀ values of 75.5 ± 11.6 and 24.2 ± 2.0 μM, respectively., Conclusions: Grapefruit juice decreases exposure of aliskiren partially via inhibition of intestinal OATP1A2.

A simple and sensitive method has been developed and validated for the determination of aliskiren (ALS) in its dosage forms and spiked plasma. The method was based on the reaction of the drug with dansyl chloride in the presence of bicarbonate solution of pH 10.5 to give a highly fluorescent derivative which was measured at 501 nm with excitition at 378 nm in dichloromethane. Different experimental parameters affecting the development of the method and stability were carefully studied and optimized. The calibration curves were linear over the concentration ranges of 100-700 and 50-150 ng/mL for standard solution and plasma, respectively. The limits of detection were 27.52 ng/mL in standard solution, 4.91 ng/mL in plasma. The developed method was successfully applied to the analysis the drug in the commercial tablets and spiked plasma samples. The mean recovery of ALS from tablets and plasma was 100.10 and 97.81%, respectively. A proposal of the reaction pathway was presented.

Background and Objectives: Renal hemodynamic effects of inhibitors of the renin-angiotensin system can increase the risk of acute kidney injury under certain conditions. The BP-lowering effects of the renin inhibitor aliskiren are sustained 3-4 weeks after withdrawal. In this study, the reversibility of the renal hemodynamic effects of aliskiren was tested., Design, Setting, Participants, & Measurements: In this open-label study, renal perfusion was measured by 1.5-T magnetic resonance imaging-arterial spin labeling in 34 subjects with arterial hypertension before aliskiren (pre-aliskiren), after 4 weeks of aliskiren treatment (300 mg), and 4-5 days (∼2.5-3.0× plasma half-life) after withdrawal (post-aliskiren)., Results: Aliskiren reduced systolic BP from 152 ± 14 to 139 ± 16 mmHg (P<0.0001), which was sustained post-aliskiren (136 ± 13 mmHg, P=1.00 versus aliskiren). Aliskiren significantly altered renal perfusion (P=0.005), increasing from 272 ± 25 pre-aliskiren to 287 ± 29 ml/min per 100 g during aliskiren (P=0.03). This increase in renal perfusion was completely reversed post-aliskiren (272 ± 26 ml/min per 100 g, P=0.03 versus aliskiren, P=0.63 versus pre-aliskiren). No changes were noted in urinary angiotensinogen levels. Plasma renin activity was reduced by aliskiren, which was sustained post-aliskiren. Angiotensin II and aldosterone were reduced by aliskiren but recovered post-aliskiren to pre-aliskiren levels., Conclusions: After withdrawal of aliskiren, the effects on BP were sustained, whereas increase in renal perfusion was reversed, which was associated with recovery of angiotensin II and aldosterone to pretreatment levels. Renal hemodynamic effects are more readily reversible than systemic effects of aliskiren.

We report a case of a patient with a rapidly progressive dementing illness and gait disturbance, in whom initial screening demonstrated a high methylmalonic acid level only, suggestive of a functional vitamin B(12) deficiency. Despite B(12) replacement therapy, he continued to decline. Further investigations demonstrated extensive signal change on magnetic resonance imaging involving grey and white matter within the corpus callosum, deep grey matter, brainstem and cerebellar peduncles, and patchy post-contrast enhancement. Laboratory testing revealed a raised erythrocyte sedimentation rate, raised anti-nuclear, intrinsic factor and lupus anticoagulant antibody titres, and a IgG kappa paraprotein. Cerebrospinal fluid was unremarkable. Bone marrow trephine biopsy showed monoclonal gammopathy of unknown significance. The patient initially responded to steroids, and underwent a brain biopsy, which was uninformative. However, 3 weeks following admission, he died due to an aspiration pneumonia. Autopsy findings were consistent with a diffuse primary central nervous system small cell B-cell lymphoma. This has been rarely reported in the medical literature, but our case exhibits typical clinical features, although patchy enhancement on imaging and the high methylmalonic acid have not been previously described. We hypothesise that his functional B(12) deficiency may have resulted from rapid cell turnover, perhaps in conjunction with the presence of intrinsic factor antibodies.

Aim: The aim of this study was to investigate the effects of orange juice and apple juice on the pharmacokinetics and pharmacodynamics of aliskiren., Methods: In a randomized crossover study, 12 healthy volunteers ingested 200 ml of orange juice, apple juice or water three times daily for 5 days. On day 3, they ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h, its excretion into urine up to 12 h and plasma renin activity up to 24 h., Results: Orange and apple juice reduced aliskiren peak plasma concentrations by 80% (95% CI 63%, 89%, P < 0.001) and 84% (95% CI 72%, 91%, P < 0.001), and the area under the plasma aliskiren concentration-time curve (AUC) by 62% (95% CI 47%, 72%, P < 0.001) and 63% (95% CI 46%, 74%, P < 0.001), respectively, but had no significant effect on its elimination half-life or renal clearance. The decreases in aliskiren AUC by orange and apple juice correlated with aliskiren AUC during the water phase (r= 0.98, P < 0.001). Plasma renin activity was 87% and 67% higher at 24 h after aliskiren during the orange juice and apple juice phases, respectively, than during the water phase (P < 0.05)., Conclusions: Orange juice and apple juice greatly reduce the plasma concentrations and renin-inhibiting effect of aliskiren, probably by inhibiting its OATP2B1-mediated influx in the small intestine. Concomitant intake of aliskiren with orange or apple juice is best avoided., (© 2011 The Authors. British Journal of Clinical Pharmacology © 2011 The British Pharmacological Society.)

Background: The direct renin inhibitor aliskiren is known to exhibit a strong antihypertensive effect. However, the organoprotective potential of aliskiren beyond its antihypertensive properties is less clear. This study investigates the antifibrotic nephroprotective effects of aliskiren in a nonhypertensive mouse model for progressive renal fibrosis., Methods: COL4A3(-/-) mice received aliskiren via osmotic minipumps. Placebo-treated animals served as controls. Therapy was initiated in 6-week-old animals already showing renal damage (proteinuria ~1 g/l, starting renal fibrosis) and lasted for 4 weeks. Six animals were sacrificed after 9.5 weeks; serum urea and proteinuria were measured. Kidneys were further investigated using histological, immunohistological, and western blot techniques. Survival until end-stage renal failure was monitored in the remaining animals., Results: COL4A3(-/-) mice did not develop hypertension. Aliskiren serum levels were in the therapeutic range (288 ± 44 ng/ml). Therapy significantly prolonged lifespan until death from renal failure by 18% compared with placebo-treated controls (78.6 ± 8.2 vs. 66.6 ± 4.9 days, P < 0.05). Similarly, therapy reduced the amount of proteinuria and serum urea. Compared with placebo-treated controls, the accumulation of extracellular matrix and renal scarring and the levels of transforming growth factor-β (TGFβ) and connective tissue growth factor (CTGF) were decreased in treated mice., Conclusions: Despite the late onset of therapy, our results indicate nephroprotective effects of the renin inhibitor aliskiren beyond its antihypertensive property in this animal model of progressive renal fibrosis. In addition to the recognized antihypertensive action of aliskiren, its antifibrotic, antiproteinuric effects demonstrated in the present study indicate that aliskiren may have potential as an important therapeutic option for chronic fibrotic diseases in humans.

In a randomized crossover study, 11 healthy volunteers took 100 mg (first dose 200 mg) of the antifungal drug itraconazole, a P-glycoprotein and CYP3A4 inhibitor, or placebo twice daily for 5 days. On day 3, they ingested a single 150-mg dose of aliskiren, a renin inhibitor used in the treatment of hypertension. Itraconazole raised the peak plasma aliskiren concentration 5.8-fold (range, 1.1- to 24.3-fold; P < .001) and the area under the plasma aliskiren concentration-time curve 6.5-fold (range, 2.6- to 20.5-fold; P < .001) but had no significant effect on aliskiren elimination half-life. Itraconazole increased the amount of aliskiren excreted into the urine during 12 hours 8.0-fold (P < .001) and its renal clearance 1.2-fold (P = .042). Plasma renin activity 24 hours after aliskiren intake was 68% lower during the itraconazole phase than during the placebo phase (P = .011). In conclusion, itraconazole markedly raises the plasma concentrations and enhances the renin-inhibiting effect of aliskiren. The interaction is probably mainly explained by inhibition of the P-glycoprotein-mediated efflux of aliskiren in the small intestine, with a minor contribution from inhibition of CYP3A4. Concomitant use of aliskiren and itraconazole is best avoided.

Gender and body weight influence the pharmacokinetics and pharmacodynamics of many drugs. This pooled analysis of 17 clinical studies evaluated the effect of gender, body mass index (BMI), body weight, and lean body weight (LBW) on the pharmacokinetics of the direct renin inhibitor aliskiren in healthy volunteers (n = 392). A separate pooled analysis of 5 clinical studies in patients with hypertension (n = 2327) assessed the influence of gender and BMI on the effects of aliskiren on plasma renin activity and blood pressure. Area under the aliskiren plasma concentration-time curve (AUC(τ)) was 22% lower and the peak aliskiren plasma concentration (C(max)) was 24% lower in men than women (P < .05). BMI was not significantly correlated with AUC(τ) (r = 0.005; P = .917); AUC(τ) was negatively correlated with body weight (r = -0.235; P < .0001) and LBW (r = -0.295; P < .0001). Results were similar for C(max). Adjusting individual aliskiren AUC(τ) and C(max) values for overall mean body weight or LBW abolished gender differences. Based on r(2) values, LBW variation accounted for 8.9% of aliskiren AUC(τ) variation. In patients with hypertension, gender and BMI did not significantly influence the effects of aliskiren on plasma renin activity or blood pressure. It was concluded that lower systemic exposure to aliskiren in men versus women relates to differences in body weight; neither gender nor body weight has clinically relevant effects on the pharmacokinetics or pharmacodynamics of aliskiren.

Purpose: This study aimed to investigate the possible effects of ABCB1 haplotypes on the pharmacokinetics and renin-inhibiting effect of aliskiren., Methods: Eleven healthy volunteers homozygous for the ABCB1 c.1236C-c.2677G-c.3435C (CGC) haplotype and 11 homozygous for the c.1236T-c.2677T-c.3435T (TTT) haplotype ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h, its excretion into urine up to 12 h, and plasma renin activity up to 24 h., Results: The ABCB1 haplotypes had no significant effect on the pharmacokinetics or renin-inhibiting effect of aliskiren. The geometric mean ratio (95% confidence interval) of aliskiren peak plasma concentration and area under the plasma concentration-time curve from 0 h to infinity in participants homozygous for the TTT haplotype to those in participants homozygous for the CGC haplotype were 1.14 (0.66, 1.96; P = 0.631) and 1.01 (0.58, 1.76; P = 0.960) respectively., Conclusions: These data suggest that the ABCB1 c.1236C-c.2677G-c.3435C and c.1236T-c.2677T-c.3435T haplotypes have no clinically meaningful effect on the pharmacokinetics of aliskiren.

The aim of this study was to evaluate pharmacokinetic parameters of fumaric acid esters (FAE) in psoriasis patients for the first time. For this prupose new HPLC assays were developed. Additionally, physicochemical parameters of FAE were determined, allowing a better interpretation of the in vivo data. In vivo, monomethylfumarate (MMF) and monoethylfumarate (MEF) were detected after t (lag) = 120 min. T (max) and c (max) of MMF were 210 min and 11.2 microM, respectively, 210 min and 5.2 microM for MEF. The half-life of MMF was 38.7 min, and 25.4 min of MEF. The AUC(0-infinity) of MMF was 172 min microg ml(-1) and 63.6 min microg ml(-1) of MEF. Data display median of three subjects. No plasma levels of dimethylfumarate (DMF) or fumaric acid (FA) were detected. The evaluation of physicochemical parameters of FAE showed that only DMF fulfils the criteria of Lipinski's rule of five. The pKa of MMF was determined as 3.63. The data of this study provide evidence that DMF is most likely absorbed out of the duodenum into the presystemic circulation and is not completely hydrolysed to MMF before uptake as assumed by others.

Purpose: This study aimed to investigate the effect of rifampicin, an inducer of CYP3A4 and P-glycoprotein, on the pharmacokinetics and pharmacodynamics of aliskiren, a renin inhibitor used in the treatment of hypertension., Methods: In a randomized crossover study, 12 healthy volunteers took 600 mg rifampicin or placebo once daily for 5 days. On day 6, they ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h and urine concentrations up to 12 h; pharmacodynamic variables were measured up to 24 h., Results: Rifampicin reduced the peak plasma aliskiren concentration (C(max)) by 39% (95% confidence interval 0.41, 0.90; P = 0.017) and the area under the plasma aliskiren concentration-time curve AUC(0-infinity) by 56% (95% confidence interval 0.35, 0.56; P < 0.001). Rifampicin had no significant effect on aliskiren elimination half-life (t(1/2)) or its renal clearance (Cl(renal)). Plasma renin activity 24 h after aliskiren intake was 61% higher during the rifampicin phase than during the placebo phase (P = 0.008)., Conclusions: Rifampicin considerably reduces the plasma concentrations and the renin-inhibiting effect of aliskiren by decreasing its oral bioavailability.

Hypertension is a major public health problem and leading cause for diseases involving cardiovascular & renal system. It is fourth largest contributor for premature deaths in developed countries and seventh largest in developing world. The major pharmacological strategies currently utilized for hypertension management include volume control with diuretics, suppression of central and peripheral sympathetic nervous system activity, vasodilatation with ion channel manipulation and blockade of renin-angiotensin-aldosterone system. Activation of the renin-angiotensin-aldosterone system in the pathogenesis of cardiovascular diseases and renal disease is well established. It also has been established that inhibition of renin-angiotensin-aldosterone system, is an effective way to intervene with pathogenesis of these disorders. Therapies like beta blockers, renin inhibitors, angiotensin converting enzyme inhibitors, angiotensin receptor blockers and aldosterone inhibitors, that inhibit renin-angiotensin-aldosterone system have proven to be highly successful for treatment of hypertension & related cardiovascular diseases. Renin inhibitors block the renin-angiotensin-aldosterone system at its origin, and thus offer a new approach to pharmacotherapy of Hypertension. Aliskiren is the first in a new class of orally active, non-peptide, low molecular weight direct renin inhibitor available for clinical use and potential new approach to the blockade of the renin-angiotensin-aldosterone system. Studies in humans demonstrate to an effectual blood Pressure lowering effect of aliskiren with placebo like tolerability, when used as monotherapy or in combination with other agents and has the potential to be useful in this wide spectrum of conditions

This study investigated the pharmacokinetics, safety, and tolerability of aliskiren administered alone or in combination with either the loop diuretic furosemide or an oral extended-release formulation of isosorbide-5-mononitrate (ISMN). In separate studies, 22 healthy subjects (ages 18-45 years) received either ISMN 40 mg or furosemide 20 mg once-daily for 3 days followed by a 3-day washout. Subjects then received aliskiren 300 mg once-daily for 7 days followed by combination therapy for 3 days. Pharmacokinetic assessments were taken at regular intervals over 24 h after dosing on the last day of each treatment period. At steady state, aliskiren AUC(tau) was decreased by 7% (geometric mean ratio [90% CI], 0.93 [0.84, 1.04]), and C(max) by 20% (0.80 [0.65, 0.97]) with furosemide coadministration compared with aliskiren administration alone. Aliskiren coadministration reduced furosemide AUC(tau) by 28% (0.72 [0.64, 0.81]) and C(max) by 49% (0.51 [0.39, 0.66]) compared with furosemide alone. Coadministration of aliskiren and ISMN was associated with only minor changes in the pharmacokinetic parameters of aliskiren (AUC(tau) 1.03 [0.90, 1.18]; C(max) 0.94 [0.69, 1.29]) and ISMN (AUC(tau) 0.88 [0.71, 1.10]; C(max) 0.94 [0.79, 1.13]). Headache and dizziness were the most common adverse events in both studies; dizziness and BP values below normal (SBP < 90 and/or DBP < 50 mmHg) were more frequent with aliskiren and ISMN coadministration than with either agent alone. Coadministration of aliskiren and ISMN had no clinically relevant effect on either aliskiren or ISMN pharmacokinetics. In conclusion, coadministration of aliskiren and furosemide reduced furosemide exposure and had a minor effect on aliskiren pharmacokinetics. The clinical significance of reduced systemic exposure to furosemide during coadministration of aliskiren is uncertain.

Objective: Hypertension and type 2 diabetes are common comorbidities, thus many patients receiving antihypertensive medication require concomitant therapy with hypoglycemic or lipid-lowering drugs. The aim of these three studies was to investigate the pharmacokinetics, safety and tolerability of aliskiren, a direct renin inhibitor for the treatment of hypertension, co-administered with the glucose-lowering agents metformin or pioglitazone or the lipid-lowering agent fenofibrate in healthy volunteers., Methods: In three open-label, multiple-dose studies, healthy volunteers (ages 18 to 45 years) received once-daily treatment with either metformin 1000 mg (n = 22), pioglitazone 45 mg (n = 30) or fenofibrate 200 mg (n = 21) and aliskiren 300 mg, administered alone or co-administered in a two-period study design. Blood samples were taken frequently on the last day of each treatment period to determine plasma drug concentrations., Results: Co-administration of aliskiren with metformin decreased aliskiren area under the plasma concentration- time curve during the dose interval (AUC(tau)) by 27% (geometric mean ratio [GMR] 0.73; 90% confidence interval [CI] 0.64, 0.84) and maximum observed plasma concentration (C(max)) by 29% (GMR 0.71; 90% CI 0.56, 0.89) but these changes were not considered clinically relevant. Co-administration of aliskiren with fenofibrate had no effect on aliskiren AUC (GMR 1.05; 90% CI 0.96, 1.16) or C(max) (GMR 1.05; 90% CI 0.80, 1.38); similarly, co-administration of aliskiren with pioglitazone had no effect on aliskiren AUC(tau) (GMR 1.05; 90% CI 0.98, 1.13) or C(max) (GMR 1.01; 90% CI 0.84, 1.20). All other AUC and C(max) GMRs for aliskiren, metformin, pioglitazone, ketopioglitazone, hydroxypioglita-zone and fenofibrate were close to unity and the 90% CI were contained within the bioequivalence range of 0.80 to 1.25., Conclusion: Co-administration of aliskiren with metformin, pioglitazone or fenofibrate had no significant effect on the pharmacokinetics of these drugs in healthy volunteers. These findings indicate that aliskiren can be co-administered with metformin, pioglitazone or fenofibrate without the need for dose adjustment.

A semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model was developed to evaluate the effects of aliskiren on the renin-angiotensin system (RAS) in humans. Mean data were extracted from a three-way crossover, placebo-controlled study. Outcome measures included the time-course of plasma renin activity (PRA) and plasma concentrations of aliskiren, active renin (AR), angiotensin I (ANG I), and angiotensin II (ANG II). The disposition of aliskiren may be best described as a two-compartment model with nonlinear elimination and distribution. The four biomarkers of RAS inhibition were co-modeled, and the AR showed a dose-dependent increase after the administration of aliskiren. This effect was described in terms of an indirect stimulatory response model in conjunction with an empirical submodel of functional adaptation. The estimated concentration of aliskiren necessary for producing 50% inhibition of PRA is 0.66 ng/ml, which is similar to in vitro estimates (0.33 ng/ml) after correction for plasma protein binding. The final and reduced models test the current hypothesis that RAS is inhibited by direct renin antagonism, and also provide suitable platforms for future clinical study design and analysis.

Background: Pharmacological interruption of the renin-angiotensin system focuses on optimization of blockade. As a measure of intrarenal renin activity, we have examined renal plasma flow (RPF) responses in a standardized protocol. Compared with responses with angiotensin-converting enzyme inhibition (rise in RPF approximately 95 mL x min(-1) x 1.73 m(-2)), greater renal vasodilation with angiotensin receptor blockers (approximately 145 mL x min(-1) x 1.73 m(-2)) suggested more effective blockade. We predicted that blockade with the direct oral renin inhibitor aliskiren would produce renal vascular responses exceeding those induced by angiotensin-converting enzyme inhibitors and angiotensin receptor blockers., Methods and Results: Twenty healthy normotensive subjects were studied on a low-sodium (10 mmol/d) diet, receiving separate escalating doses of aliskiren. Six additional subjects received captopril 25 mg as a low-sodium comparison and also received aliskiren on a high-sodium (200 mmol/d) diet. RPF was measured by clearance of para-aminohippurate. Aliskiren induced a remarkable dose-related renal vasodilation in low-sodium balance. The RPF response was maximal at the 600-mg dose (197+/-27 mL x min(-1) x 1.73 m(-2)) and exceeded responses to captopril (92+/-20 mL x min(-1) x 1.73 m(-2); P<0.01). Furthermore, significant residual vasodilation was observed 48 hours after each dose (P<0.01). The RPF response on a high-sodium diet was also higher than expected (47+/-17 mL x min(-1) x 1.73 m(-2)). Plasma renin activity and angiotensin levels were reduced in a dose-related manner. As another functional index of the effect of aliskiren, we found significant natriuresis on both diets., Conclusions: Renal vasodilation in healthy people with the potent renin inhibitor aliskiren exceeded responses seen previously with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. The effects were longer lasting and were associated with significant natriuresis. These results indicate that aliskiren may provide more complete and thus more effective blockade of the renin-angiotensin system.

1. Initial attempts to inhibit renin in humans have faced numerous difficulties. Molecular modelling and X-ray crystallography of the active site of renin have led to the development of new orally active renin inhibitors, such as aliskiren. 2. Aliskiren has a low bioavailability (between 2.6 and 5.0%) compensated by its high potency to inhibit renin (IC50: 0.6 nmol/L) and a long plasma half-life (23-36 h), which makes it suitable for once-daily dosing. 3. The once-daily administration of aliskiren to hypertensive patients lowers BP as strongly as standard doses of established angiotensin II type 1 (AT1) receptor blockers (losartan, valsartan, irbesartan), hydrochlorothiazide, angiotensin converting enzyme inhibitors (ramipril and lisinopril) or long acting calcium channel blockers (amlodipine). In combination therapy, aliskiren further decreases blood pressure when combined with either hydrochlorothiazide, amlodipine, irbesartan or ramipril. 4. The biochemical consequences of renin inhibition differ from those of angiotensin I-converting enzyme (ACE) inhibition and Ang II antagonism, particularly in terms of angiotensin profiles and interactions with the bradykinin-nitric oxide-cyclic guanosine monophosphate pathway and possibly the (pro)renin receptor. 5. Blockade of the renin angiotensin system (RAS) with ACE inhibitors, AT1 receptor blockers or a combination of these drugs has become one of the most successful therapeutic approaches in medicine. However, it remains unclear how to optimize RAS blockade to maximize cardiovascular and renal benefits. In this context, renin inhibition to render the RAS fully quiescent is a new possibility requiring further study.

Objective: Aliskiren is the first in a new class of orally effective direct renin inhibitors approved for the treatment of hypertension. This multiple-dose study investigated the potential for pharmacokinetic interactions between aliskiren and three drugs, each predominantly eliminated by a different clearance/metabolic pathway: allopurinol (glomerular filtration), celecoxib (cytochrome P450 metabolism) and cimetidine (P-glycoprotein and organic anion/cation transporters)., Research Design and Methods: Three open-label, multiple-dose studies in healthy subjects investigated possible pharmacokinetic interactions between aliskiren 300 mg od and allopurinol 300 mg od (n = 20), celecoxib 200 mg bid (n = 22), or cimetidine 800 mg od (n = 22). Subjects received aliskiren alone or co-administered with allopurinol, celecoxib or cimetidine. Allopurinol and celecoxib were also administered alone and in combination with aliskiren. Plasma drug concentrations were determined by LC/MS/MS., Results: Co-administration of aliskiren with allopurinol had no effect on allopurinol AUC(tau) (ratio of geometric means 0.93 [90% CI, 0.88, 0.98]) or oxypurinol AUC(tau) (mean ratio 1.12 [90% CI, 1.08, 1.16]) and C(max) (mean ratio 1.08 [90% CI, 1.04, 1.13]), with 90% CI within the bioequivalence range 0.80-1.25, and a minor effect on allopurinol C(max) (mean ratio 0.88 [90% CI, 0.78, 1.00]). Aliskiren co-administration had no effect on AUC(tau) or C(max) of celecoxib (mean ratios and 90% CI within range 0.80-1.25). Neither allopurinol nor celecoxib significantly altered aliskiren AUC(tau) or C(max) (geometric mean ratios 0.88-1.02 with 90% CI including 1.00, but with some 90% CI outside the 0.80-1.25 range due to high variability). Co-administration of aliskiren with cimetidine increased aliskiren AUC(tau) by 20% (mean ratio 1.20 [90% CI, 1.07, 1.34]) and C(max) by 25% (mean ratio 1.25 [90% CI, 0.98, 1.59])., Conclusions: In this multiple-dose study, aliskiren showed no clinically relevant pharmacokinetic interactions when co-administered with allopurinol, celecoxib or cimetidine in healthy subjects.

Aliskiren (2(S),4(S),5(S),7(S)-N-(2-carbamoyl-2-methylpropyl)-5-amino-4-hydroxy-2,7-diisopropyl-8-[4-methoxy-3-(3-methoxypropoxy)phenyl]-octanamid hemifumarate) is the first in a new class of orally active, nonpeptide direct renin inhibitors developed for the treatment of hypertension. The absorption, distribution, metabolism, and excretion of [(14)C]aliskiren were investigated in four healthy male subjects after administration of a single 300-mg oral dose in an aqueous solution. Plasma radioactivity and aliskiren concentration measurements and complete urine and feces collections were made for 168 h postdose. Peak plasma levels of aliskiren (C(max)) were achieved between 2 and 5 h postdose. Unchanged aliskiren represented the principal circulating species in plasma, accounting for 81% of total plasma radioactivity (AUC(0-infinity)), and indicating very low exposure to metabolites. Terminal half-lives for radioactivity and aliskiren in plasma were 49 h and 44 h, respectively. Dose recovery over 168 h was nearly complete (91.5% of dose); excretion occurred almost completely via the fecal route (90.9%), with only 0.6% recovered in the urine. Unabsorbed drug accounted for a large dose proportion recovered in feces in unchanged form. Based on results from this and from previous studies, the absorbed fraction of aliskiren can be estimated to approximately 5% of dose. The absorbed dose was partly eliminated unchanged via the hepatobiliary route. Oxidized metabolites in excreta accounted for at least 1.3% of the radioactive dose. The major metabolic pathways for aliskiren were O-demethylation at the phenyl-propoxy side chain or 3-methoxy-propoxy group, with further oxidation to the carboxylic acid derivative.

This open-label, multicenter study compared the pharmacokinetics and safety of the oral direct renin inhibitor aliskiren in 29 elderly (>or=65 years) and 28 young (18-45 years) healthy subjects. Plasma drug concentrations were determined for up to 168 hours following a single 300-mg oral dose of aliskiren. In elderly compared with young subjects, AUC(0-infinity) was 57% higher (ratio of geometric means 1.57, 90% confidence interval: 1.19, 2.06; P = .008) and C(max) was 28% higher (1.28, 90% confidence interval: 0.91, 1.79; P=.233). Other parameters, including t(max) and Vd/F, were similar between age groups. No differences in aliskiren exposure were observed between subjects ages 65 to 74 years (n=16) and >or=75 years (n=13). Aliskiren was well tolerated by all age groups, including the very elderly. In conclusion, aliskiren exposure is modestly increased in elderly subjects. Based on its wide therapeutic index and shallow dose response for blood pressure lowering, no initial dose adjustment should be needed for elderly patients.

Thiazide diuretics, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers all cause reactive rises in plasma renin activity. We hypothesized that renin inhibition with aliskiren would prevent this reactive rise and also enhance blood pressure lowering. In 3 open-label studies in which blood pressure was assessed with ambulatory measurement, aliskiren was administered to patients with mild-to-moderate hypertension in combination with hydrochlorothiazide (n=23), ramipril (n=21), or irbesartan (n=23). In the diuretic combination study, the addition of 25 mg of hydrochlorothiazide to 150 mg of aliskiren daily for 3 weeks significantly lowered daytime pressure, compared with aliskiren monotherapy (systolic/diastolic mean change from baseline [SEM]: daytime: -18.4 [2.1]/ -10.6 [1.7] versus -10.4 [1.8]/-5.8 [1.4]; nighttime: -15.6 [2.7]/-8.1 [1.8] versus -8.8 [2.9]/-5.0 [2.2]). In the angiotensin-converting enzyme inhibitor combination study, the addition of 75 or 150 mg of aliskiren to 5 mg of ramipril alone for 3 weeks further lowered both daytime and nighttime pressures compared with ramipril monotherapy (daytime: -10.5 [2.9]/-8.1 [2.1] and -14 [3.7]/-8.7 [2.3] versus -6.1 [2.4]/-5.9 [1.5]; nighttime: -8.1 [2.6]/-5.3 [2.4] and -9.6 [3.4]/-5.3 [2.4] versus -2 [2.3]/-0.7 [2.2]). In the angiotensin receptor blocker combination study, the addition of 75 or 150 mg of aliskiren to 150 mg of irbesartan alone, for 3 weeks, resulted in significantly lower nighttime pressures compared with irbesartan monotherapy (daytime: -14.8 [2]/-8.2 [1.3] and -13.3 [1.6]/-6.8 [0.9] versus -11.4 [1.6]/-6.5 [1.1]; nighttime: -16.1 [2.4]/-8.6 [1.7] and -13.2 [2.7]/-7.2 [1.9] versus -9.0 [2.5]/-4.7 [1.9]). Aliskiren (150 mg) alone significantly inhibited plasma renin activity by 65% (P<0.0001). Ramipril and irbesartan monotherapy caused 90% and 175% increases in plasma renin activity, respectively. By contrast, when aliskiren was coadministered with hydrochlorothiazide, ramipril, or irbesartan, plasma renin activity did not increase but remained similar to baseline levels or was decreased (combination therapy versus untreated; median [interquartile range]; aliskiren and hydrochlorothiazide: 0.4 [0.2 to 1.1] versus 0.7 [0.5 to 1.3]; ramipril and aliskiren: 0.5 [0.3 to 0.9] versus 0.6 [0.5 to 0.8]; irbesartan and aliskiren: 0.4 [0.2 to 0.9] versus 0.6 [0.4 to 0.9]). These results suggest that renin inhibition with aliskiren in these combinations increases renin-angiotensin system suppression, improves 24-hour blood pressure control, and may ultimately provide better end-organ protection in patients with hypertension.

Aliskiren is the first in a new class of orally active, direct renin inhibitors for the treatment of hypertension. This open-label, nonrandomized, single-center, parallel-group study compared the pharmacokinetics and safety of a single 300-mg oral dose of aliskiren in patients with mild, moderate, or severe hepatic impairment to that in healthy subjects. When pooled across subgroups, there were no significant differences between patients with hepatic impairment and healthy subjects in aliskiren AUC(0-infinity) (ratio of geometric means, 1.12; 90% confidence interval, 0.85, 1.48) or Cmax (mean ratio, 1.19; 90% confidence interval, 0.84, 1.68), and there was no correlation between severity of hepatic impairment and either AUC(0-infinity) or Cmax. Aliskiren was well tolerated by healthy subjects and patients with hepatic impairment. In conclusion, hepatic impairment has no significant effect on the pharmacokinetics of aliskiren following single-dose administration, and dosage adjustment is unlikely to be needed in patients with liver disease.

Aims: Aliskiren is the first in a new class of orally effective renin inhibitors for the treatment of hypertension. This study compared the pharmacokinetic and pharmacodynamic properties of aliskiren in Japanese and Caucasian subjects., Methods: In this open-label, single-centre, parallel-group, single- and multiple-dose study, 19 Japanese and 19 Caucasian healthy young male subjects received a single 300-mg oral dose of aliskiren on day 1 and then aliskiren 300 mg once daily on days 4-10. Blood samples were collected for the measurement of plasma aliskiren concentration, plasma renin concentration (PRC) and plasma renin activity (PRA)., Results: Pharmacokinetic parameters were comparable in Japanese and Caucasian subjects following administration of a single dose of aliskiren {ratio of geometric means: C(max) 1.12 [90% confidence interval (CI) 0.88, 1.43]; AUC(0-72 h) 1.19 [90% CI 1.02, 1.39]} and at steady state [mean ratio: C(max) 1.30 (90% CI 1.00, 1.70); AUC(0-tau) 1.16 (90% CI 0.95, 1.41)]. There was no notable difference in the plasma half-life of aliskiren between Japanese and Caucasian groups (29.7 +/- 10.2 h and 32.0 +/- 6.6 h, respectively). At steady state, peak PRC level and AUC for the concentration-time plot were not significantly different between Japanese and Caucasian subjects (P = 0.64 and P = 0.80, respectively). A single oral dose of aliskiren significantly reduced PRA to a similar extent in Japanese and Caucasian subjects (by 87.5% and 85.7%, respectively, compared with baseline; P < 0.01). Aliskiren was well tolerated by both ethnic groups., Conclusions: The oral renin inhibitor aliskiren demonstrated similar pharmacokinetic and pharmacodynamic properties in Japanese and Caucasian subjects.

The patients affected by vitamin B12-unresponsive methylmalonic acidemia (MMA) on the long run develop chronic renal disease with interstitial nephropathy and progressive renal insufficiency. The mechanism of nephrotoxicity in vitamin B12-unresponsive MMA is not yet known. Chronic hyporeninemic hypoaldosteronism has been found in many cases of methylmalonic acidemia, hyperkalemia and renal tubular acidosis type 4. We report 2 patients affected by B12-unresponsive methylmalonic acidemia diagnosed at the age of 23 months and 5 years, respectively, with normal glomerular filtration and function. They showed hyporeninemic hypoaldosteronism and significant hyperkalemia requiring sodium potassium exchange resin (Kayexalate) therapy after an episode of metabolic decompensation leading to diagnosis of MMA. In both children, hyporeninemic hypoaldosteronism and hyperkalemia disappeared after 6 months of good metabolic control.

Background: The renin system is an attractive target for antihypertensive therapy in patients with diabetes mellitus. However, diabetes is associated with changes in gastrointestinal, renal and hepatic function that may affect the absorption and disposition of oral drugs. This study compared the pharmacokinetics and pharmacodynamics of the orally active direct renin inhibitor, aliskiren, in healthy volunteers and patients with type 2 diabetes., Methods: This was an open-label study conducted in 30 patients with type 2 diabetes and 30 healthy volunteers matched for age, bodyweight and race. Following a 10-hour fast, all participants received a single oral dose of aliskiren 300mg. Blood samples were taken at frequent intervals for 96 hours post-dose for determination of plasma concentrations of aliskiren (using a high-performance liquid chromatography-tandem mass spectroscopy method). Plasma renin activity (PRA) and renin concentration (RC) were also measured for 24 hours after dosing., Results: Aliskiren exhibited similar pharmacokinetics in patients with type 2 diabetes and healthy volunteers. Exposure to aliskiren was slightly higher in patients with type 2 diabetes compared with healthy volunteers (mean area under the plasma concentration-time curve from 0 to 24 hours 1859 vs 1642 ng . h/mL; maximum observed plasma drug concentration 394 vs 348 ng/mL), while apparent clearance corrected for bioavailability was slightly lower (205 vs 234 L/h) and elimination half-life slightly longer (44 vs 39.9 hours), but there were no statistically significant differences for any pharmacokinetic parameters. There was no significant correlation between glycaemic control (% glycosylated haemoglobin) and any of the measured pharmacokinetic parameters in patients with type 2 diabetes. Aliskiren caused sustained suppression of PRA for at least 24 hours after dosing despite increasing RC; there were no major differences in the pharmacodynamic effects of aliskiren between patients with type 2 diabetes and healthy volunteers. Aliskiren was well tolerated in both patient groups, with no clinically significant changes in laboratory values and a low risk of adverse events., Conclusion: Aliskiren showed a similar pharmacokinetic profile in healthy volunteers and patients with type 2 diabetes, and administration of a single oral 300 mg dose of aliskiren was well tolerated by both patients and healthy volunteers. The pharmacodynamic effects of aliskiren were also similar in healthy volunteers and diabetic patients, with sustained inhibition of renin system activity observed for at least 24 hours after dosing.

Objective: Aliskiren is the first in a new class of orally effective renin inhibitors for the treatment of hypertension. This study investigated the interaction profile of aliskiren, which is of clinical importance because hypertensive patients often require concomitant drug therapy for associated comorbidities., Methods: Four separate studies investigated the pharmacokinetic interaction between single oral doses of aliskiren and lovastatin, atenolol, celecoxib or cimetidine, respectively. All studies involved healthy male volunteers aged 18-45 years. In 3 studies, subjects (n = 15 in each study) received single doses of aliskiren 150 mg alone, the test drug alone (lovastatin 40 mg, atenolol 100 mg or celecoxib 200 mg), or both drugs in combination, according to a 3-period crossover design. In the cimetidine study (n = 12), aliskiren 150 mg was administered alone or concomitantly with cimetidine 800 mg according to a two-period crossover design. Plasma concentrations of aliskiren and test drugs were determined by liquid chromatography and mass spectrometry methods. Pharmacokinetic parameters were derived from these data., Results: Mean AUC and t1/2 for aliskiren were not significantly changed by lovastatin, atenolol or celecoxib (< 10% difference between treatments). Aliskiren mean Cmax was not affected by either lovastatin or atenolol, although a non-significant 36% increase was observed with celecoxib. Modest, non-significant increases in aliskiren systemic availability followed coadministration with cimetidine (aliskiren mean AUC, Cmax and t1/2 increased by 17%, 19% and 15%, respectively). Aliskiren coadministration had no significant effect on the disposition of lovastatin, atenolol or celecoxib., Conclusions: Overall, single doses of aliskiren showed no evidence of clinically important pharmacokinetic interactions with lovastatin, atenolol, celecoxib or cimetidine.

We report the fourth case of combined D-and L-2-hydroxyglutaric aciduria presenting with neonatal encephalopathy and subependymal cysts.

A fumarase-deficient patient expressed a novel phenotype of congenital cerebral ventricular dilatation and periventricular cysts. The patient was a compound heterozygote for two mutations that are the only ones among the 12 published mutations that have been found in multiple, unrelated, fumarase-deficient patients.

Background: Psoriasis is a chronic inflammatory skin disease that can be successfully treated with a mixture of fumaric acid esters (FAE) formulated as enteric-coated tablets for oral use. These tablets consist of dimethylfumarate (DMF) and salts of monoethylfumarate (MEF) and its main bioactive metabolite is monomethylfumarate (MMF). Little is known about the pharmacokinetics of these FAE. The aim of the present study was to investigate the hydrolysis of DMF to MMF and the stability of MMF, DMF and MEF at in vitro conditions representing different body compartments., Results: DMF is hydrolyzed to MMF in an alkaline environment (pH 8), but not in an acidic environment (pH 1). In these conditions MMF and MEF remained intact during the period of analysis (6 h). Interestingly, DMF was hardly hydrolyzed to MMF in a buffer of pH 7.4, but was rapidly hydrolyzed in human serum having the same pH. Moreover, in whole blood the half-life of DMF was dramatically reduced as compared to serum. The concentrations of MMF and MEF in serum and whole blood decreased with increasing time. These data indicate that the majority of the FAE in the circulation are metabolized by one or more types of blood cells. Additional experiments with purified blood cell fractions resuspended in phosphate buffered saline (pH 7.4) revealed that at concentrations present in whole blood monocytes/lymphocytes, but not granulocytes and erythrocytes, effectively hydrolyzed DMF to MMF. Furthermore, in agreement with the data obtained with the pure components of the tablet, the enteric-coated tablet remained intact at pH 1, but rapidly dissolved at pH 8., Conclusion: Together, these in vitro data indicate that hydrolysis of DMF to MMF rapidly occurs at pH 8, resembling that within the small intestines, but not at pH 1 resembling the pH in the stomach. At both pHs MMF and MEF remained intact. These data explain the observation that after oral FAE intake MMF and MEF, but not DMF, can be readily detected in the circulation of human healthy volunteers and psoriasis patients.

The dynamics of total calcium concentration in blood of rat females with osteoporosis caused experimentally after applying it in the form of fumarate was determined. The fumarate was applied in just one dose by the means of stomach tube at the dose of teoporoz&#95; 4.28 mg of calcium/100 g of body mass. The total calcium concentration in blood was determined: 0; 1; 2; 3; 5 i 7 h after application. It was observed that one hour after application calcium concentration in control group increased by 19.3%, and in the group of animals after ovariectomy it decreased by 6.7% (P < 0.001). After 2 h calcium concentration in both groups returned to its initial state, and after 3 hours three next decrease in relation to initial time by 10% occurred in the control group and by 4% in the group after ovariectomy. Between 4 h and 7 h after administration calcium concentration in both groups of animals was even and it was maintaining at the constant level in the range 2.248-2.172 mM/l.