UGT1A3 and Sex Are Major Determinants of Telmisartan Pharmacokinetics-A Comprehensive Pharmacogenomic Study.

To investigate how variability in multiple pharmacokinetic genes associates with telmisartan exposure, we determined telmisartan single-dose (40 mg) pharmacokinetics and sequenced 379 genes in 188 healthy volunteers. Intronic UGT1A variants showed the strongest associations with the area under the plasma concentration-time curve from zero hours to infinity (AUC0-∞ ) and peak plasma concentration (Cmax ) of telmisartan. These variants were strongly linked with the increased function UGT1A3*2 allele, suggesting that it is the causative allele underlying these associations. In addition, telmisartan plasma concentrations were lower in men than in women. The UGT1A3*2 was associated with a 64% and 63% reduced AUC0-∞ of telmisartan in UGT1A3*2 heterozygous and homozygous men, respectively (P = 1.21 × 10-16 and 5.21 × 10-8 ). In women, UGT1A3*2 heterozygosity and homozygosity were associated with 57% (P = 1.54 × 10-11 ) and 72% (P = 3.31 × 10-15 ) reduced AUC0-∞ , respectively. Furthermore, a candidate gene analysis suggested an association of UGT1A3*3 and the SLCO1B3 c.767G>C missense variant with telmisartan pharmacokinetics. A genotype score, which reflects the effects of sex and genetic variants on telmisartan AUC0-∞ , associated with the effect of telmisartan on diastolic blood pressure. These data indicate that sex and UGT1A3 are major determinants and suggest a role for OATP1B3 in telmisartan pharmacokinetics.

A vinylpyrrolidone-based thin film microextraction in combination with direct solid-state spectrofluorimetry for determination of sartans in human plasma.

A vinylpyrrolidone-ethylene glycol dimethacrylate-acrylic acid thin film was prepared on a polypropylene guard and its formulation was optimized for application in thin film microextraction followed by direct solid-state spectrofluorimetry method. The surface morphology, fluorescence property and extraction performance of the thin film were investigated systematically. The intra- and inter-batch reproducibilities of thin film fabrication were obtained 2.3 and 4.2%, respectively. The lifetime of each prepared thin film was 30 times with a relative standard deviation of less than 1.4%. The developed method was optimized for extraction of some sartans as angiotensin II receptors antagonist (including losartan, valsartan, and olmesartan) which have been used to control hypertension as the main causes of cardiovascular disease. The optimum extraction conditions achieved at 2- (for losartan) and 4- (for valsartan and olmesartan) sample pH, 500-rpm rotation rate and 30-min extraction time for all three analytes. At the optimum conditions, analyses of losartan, valsartan, and olmesartan were validated in the human plasma matrix. Broad linearity ranges with determination coefficients of more than 0.999 were achieved for each calibration curve. Limit of detection of the method was 0.5 ng mL-1 for all three analytes. The intra- and inter-day accuracies and precisions of the developed method were evaluated in spiked plasma samples at three concentration levels of each analyte with high recoveries of 95-101% and relative standard deviations less than 6%. This method provides a simple, sensitive, fast, and high-throughput analysis method with the possibility of effective extraction of at least 40 samples simultaneously without the necessity of protein precipitating, desorption, and solvent evaporation steps.

Development and validation of reverse phase HPLC method for determination of angiotensin receptor blocking agent irbesartan in plasma.

A sensitive, reproducible and modest analytical procedure was developed and validated for evaluation of irbesartan in human plasma. LLE (Liquid-Liquid extraction) of the drug was carried out with acetonitrile (1:1 v/v). Chromatographic separation of irbesartan was conducted by the help of 4.0mm × 25cm column having L1 packing from plasma and mobile phase utilizing HPLC. The mobile phase comprise of phosphate buffer and acetonitrile in a ratio of 67:33 v/v. The flow rate was set at 1ml/minute and the detector at a wavelength of 220 nm. The resolution of irbesartan was well performed from plasma components. This method was validated and demonstrated linearity with a concentration range of 0.1to 6µg/ml of irbesartan in plasma. Intra-day, inter-day accuracy was found 89.33% to 96.37% while intra-day, inter-day precision was found within the limit of 0.02 and 2.15 respectively. The mean recovery of irbesartan was 97.28%. The efficacy of extraction was proved by above-mentioned results. In plasma, the 0.05 and 0.1µg/ml dilutions were exhibited as the LOD and LOQ of irbesartan. Stability studies disclosed that irbesartan showed stability at -20°C storage.

Development and validation of HPLC method for the determination of Candesartan in human plasma.

Candesartan (CAN), an ARB-blocker, antihypertensive, was analyzed in human plasma by a simple, accurate and precise RP-HPLC (reverse phase-High performance liquid chromatography assay method which was then validated for its accuracy, specificity and precision. The mobile phase has a constitution of acetone, diethylamine and distilled water, while Phosphoric acid was used to adjust the pH to 2.5±0.1. This mobile phase was run at 1.1ml/min and the fluorescence wavelength was set to 392 nm. A C-18 HPLC, column particle size (5 µm) Mediterranean Sea ® L x 1.D. 25cm x 4.6 mm (Supelcosil) , with auto sampler injection volume of 30µl ,an internal standard Valsartan was utilized for chromatographic detection. Candesartan took a retention time of 6±0.5 minutes. This method was validated by the parameters of selectivity, accuracy, precision, repeatability, reproducibility, recovery, linearity and stability. Candesartan's calibration curves were found to be linear in the range of 200ng/ml to 3.125ng/ml and the coefficient of determination (r2) was found to be 0.99. Analytical recovery obtained was above 88%. Hence, this method has been found to be useful for determining Candesartan in plasma.

No pharmacokinetic interactions between candesartan and amlodipine following multiple oral administrations in healthy subjects.

PURPOSE: To evaluate the pharmacokinetics and pharmacodynamics of candesartan and amlodipine in the absence and presence of each other in healthy subjects. METHODS: This study consisted of two parts: part 1, the effect of amlodipine on candesartan; part 2, the effect of candesartan on amlodipine. Each part was designed as a randomized, open-label, two-sequence, two-period, two-intervention crossover study with 20 subjects and performed separately in different populations. Pharmacokinetic assessments were performed over 48 hours for candesartan in part 1 and 72 hours for amlodipine in part 2 after drug administration on Day 10. Safety data included the results of physical examinations, clinical laboratory tests, vital signs, an electrocardiogram, and adverse events. RESULTS: For both candesartan and amlodipine, the 90% confidence intervals for the geometric mean ratios of area under the concentration-time curve from time zero to the time of dosing interval of 24 hours and maximum concentration after drug administration fell within the bioequivalence acceptance criteria. Although this study was conducted in normotensive subjects, blood pressure lowering effects were observed in all intervention groups and co-administration of candesartan and amlodipine reduced blood pressure more than amlodipine alone, but similar to candesartan alone. No serious adverse event was reported throughout the study, and all treatment emergent adverse events were mild to moderate in severity and were recovered without sequelae. CONCLUSION: Co-administration of candesartan and amlodipine did not change the systemic exposure of each drug alone in healthy subjects. The administration of candesartan 32 mg alone, amlodipine 10 mg alone, and co-administration of candesartan and amlodipine were well tolerated during the study.

Formulation and In Vitro, In Vivo Correlation Between Two Candesartan Cilexetil Tablets.

In this study, the in vitro and in vivo interchangeability between generic candesartan 16 mg and the branded formulation was assessed. The in vitro release of these products was conducted in 3 pH media (1.2, 5.0, and 6.8), and similarity factors (f2 ) were calculated. This bioequivalence study was a randomized, 2-period crossover study that included 42 healthy adult male subjects under fasting conditions with a 9-day washout. The pharmacokinetic (PK) parameters AUC0-last , AUC0-∞ , and Cmax , tmax , and the elimination half-life time were assessed based on the plasma concentrations of candesartan, using a newly developed and validated liquid chromatography-tandem mass spectrometry bioanalytical method with acceptable degrees of linearity, sensitivity, precision, and accuracy. The geometric mean (ng·h/mL) of the AUC0-∞ for the test and brand was 1595.49 and 1620.54, respectively, and the Cmax (ng/mL) was 160.91 and 160.88, respectively. The 90%CIs of geometric mean ratios (test-to-reference ratios) were 98.26%, 98.45%, and 99.86% for AUC0-last , AUC0-∞ , and Cmax respectively. These PK parameters lie within the US Food and Drug Administration- and European Medicines Agency-specified bioequivalence limit (80%-125%). Both products were well tolerated by all the subjects. The tested drug product was bioequivalent to the reference drug and had the same safety profile.

Chromatographic method development and validation for the determination of valsartan in biological fluid.

A swift, precise and simple HPLC bioanalytical technique with UV detection was established and validated for quantitative estimation of valsartan in human plasma. The analyte was separated from plasma by protein precipitation with acetonitrile and chromatographically separated on Zorbax SB-C18 (5µm, 4.6mm × 15cm) column. The solvent mixture system consisting of acetonitrile, water and glacial acetic acid (40:59:1 v/v), was pumped using isocratic mode at 1mL/min flow rate. Samples' detection of drug was made spectrophotometrically at a wavelength of 264nm. The analyte response was instituted to be linear from 0.06 to 8µg/mL with a regression value of 0.999. The accuracy of the proposed method was ranged between 97.2-100.3% with 5% RSD. The analytical recovery (>95%) was consistently observed and satisfactory sample stability was also found at different environmental conditions. In conclusion the reported bio-analytical method is easy and robust that was successfully utilized in estimation of valsartan in a pharmacokinetic study.

Bioequivalence Study of a New Fixed-dose Combination Tablet Containing S-Amlodipine Nicotinate and Olmesartan Medoxomil in Healthy Korean Male Subjects.

PURPOSE: A fixed-dose combination (FDC) pill of amlodipine (relatively old calcium channel blocker as dihydropyridine) and olmesartan (relatively new angiotensin II receptor blocker) is used for hypertension that is not adequately controlled with a single-formulation drug. Because the FDC is a one-pill formulation, and amlodipine and olmesartan have different mechanisms of action, it is expected to improve patients' medication compliance and have an increased blood pressure-lowering efficacy. The purpose of this study was to assess the safety profile and the bioequivalence of two different FDC formulations [amlodipine besylate/olmesartan medoxomil 10/40 mg (reference product) and S-amlodipine nicotinate/olmesartan medoxomil 5/40 mg (test product)]. METHODS: A randomized, open-label, single-dose, 2-treatment, 2-way, and 2-period crossover study, including a 3-week washout period, was performed in 32 healthy Korean male volunteers. To analyze the concentration of S-amlodipine or olmesartan, plasma samples were collected up to 144 hours after the dose for S-amlodipine and 48 hours after the dose for olmesartan. Pharmacokinetic parameters, including the Cmax and the area under the curve from time 0 to the last measurable concentration (AUC0-last) for the time versus concentration plot, were calculated. Analysis of variance for bioequivalence was conducted using Cmax and AUC0-last converted to log scale, and the mean ratios and 90% CIs were determined. Safety data included analysis of adverse events (AEs), vital signs, physical examinations, clinical laboratory test, and 12-lead ECGs. FINDINGS: Of the 32 enrolled participants, 29 healthy volunteers completed the study. For both S-amlodipine and olmesartan, the main pharmacokinetic parameters were all within the acceptable range for regulatory bioequivalence. The 90% CIs for the geometric mean ratios of Cmax and AUC0-last were 0.8766 to 0.9760 and 0.8288 to 0.9224, respectively, for S-amlodipine and 0.9097 to 1.1229 and 0.8904 to 1.0407, respectively, for olmesartan. Hypotension was the most frequent AE, and it was observed in 4 volunteers with the test product and 7 volunteers with the reference product. Both the test and reference formulations were well tolerated. IMPLICATIONS: The present study demonstrates that the newly developed FDC product (test drug) and the conventional FDC product (reference drug) have comparable pharmacokinetic characteristics in healthy adult male volunteers. Both the test and reference products indicated good tolerance in this population, and no serious AEs were observed.

Pharmacokinetic and bioequivalence study comparing a candesartan cilexetil/rosuvastatin calcium fixed-dose combination with the concomitant administration of candesartan cilexetil and rosuvastatin calcium in healthy Korean subjects
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CONTEXT: A fixed-dose combination (FDC) of candesartan and rosuvastatin was recently developed for the treatment of cardiovascular disease and expected to enhance patient compliance. OBJECTIVE: This study was performed to compare the single-dose pharmacokinetic properties and tolerability of DP-R208 (candesartan and rosuvastatin FDC) to those of each component administered alone in healthy Korean male volunteers. MATERIALS AND METHODS: A total of 40 healthy Korean volunteers were enrolled in this randomized, open-label, single-dose, two-treatment, two-way crossover study. During each treatment period, subjects received the test formulation (FDC tablet containing candesartan and rosuvastatin) or reference formulation (co-administration of candesartan and rosuvastatin). Plasma samples were collected pre-dose and at 0.5, 1, 2, 3, 4, 5, 6, 8, 12, 24, and 48 hours post-dose. Safety and tolerability were assessed by the evaluation of adverse events (AEs), physical examinations, laboratory assessments, 12-lead electrocardiograms (ECGs), and vital sign measurements. RESULTS: The 90% confidence intervals (CIs) of the geometric least-square mean ratios of Cmax, AUClast, and AUCinf were 0.86 - 1.00, 0.92 - 1.04, and 0.92 - 1.03 for candesartan, and 0.88 - 1.06, 0.91 - 1.08, and 0.91 - 1.03 for rosuvastatin, respectively. All of the AEs were mild, and there was no significant difference in the incidence of AEs between the formulations. Furthermore, the pharmacokinetic properties of the test and reference formulations met the regulatory criteria for bioequivalence. Discussion and conclusion: Both formulations were safe and well tolerated, and no significant difference was observed in the safety assessments of the treatments.
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Quantitative analysis of valsartan by two-dimensional liquid chromatography (2D-HPLC) and its application in a bioequivalence study in Chinese volunteers
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PURPOSE: To develop a sensitive, two-dimensional liquid chromatography (2D-LC) method for determination of valsartan, applied to investigate bioequivalence of two valsartan tablets in Chinese volunteers under fasting condition. METHODS: A full automatic 2D-HPLC system was used to quantify valsartan in human plasma. The analytes were extracted by protein precipitation, using telmisartan as internal standard. The analytical method was applied in a randomized, crossover bioequivalence study of valsartan tablets; the study enrolled 18 Chinese volunteers (12 were men and 6 were women). The subjects received a single 160-mg dose of test or reference preparation with 7-days of washout under fasting state. Plasma samples were collected, pharmacokinetic parameters were obtained and the bioequivalence was evaluated. RESULTS: The calibration range was 9.2 - 4213.8 ng×mL-1. Inter- and intraprecision was less than 7.0%, and accuracies ranged from 99.5 to 103.8%. The extraction recovery for valsartan varied between 89.3 and 97.8%, and the stability in all conditions was excellent. The 90% CI of AUC0→36h and Cmax were 96.5 - 109.4% and 94.2 - 108.6%, respectively. The relative bioavailability was 103.9 ± 15.7%. No gender difference was observed in pharmacokinetic parameters. CONCLUSIONS: A sensitive 2D-HPLC method was established for the estimation of valsartan in human plasma and successfully applied in a bioequivalence study of valsartan, which suggests that these two formulations can be assumed to be bioequivalent.
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Is a deuterated internal standard appropriate for the reliable determination of olmesartan in human plasma?

A right choice of the internal standard is one of the most challenging tasks during bioanalytical method development. Surprisingly, among the HPLC-MS methods for the determination of a cardiovascular drug olmesartan in plasma only structural analogues or similar compounds were used as internal standards. We have tried to answer the question whether the stable isotope labelled (deuterated) internal standard, as recommended by regulatory agencies, can be used for the reliable determination of olmesartan in human plasma. An HPLC-MS method using this standard in a simplified liquid-liquid extraction procedure led to accurate and precise results in the linearity range of 5-2500ng/mL. The method is well suited for pharmacokinetic studies following a single 40mg oral dose of olmesartan medoxomil in humans. The method was fully validated according to international guidelines and successfully applied in a bioequivalence study in humans. The use of deuterated olmesartan as the internal standard afforded a reliable tool for regulatory bioanalysis that can indirectly contribute to therapy efficacy and improve the safety of patients treated with generic medicines.

The influence of dietary sodium content on the pharmacokinetics and pharmacodynamics of fimasartan.

A low sodium diet enhances the hemodynamic effect of renin-angiotensin system blockers. It was suggested that the substrates of P-glycoprotein or cytochrome P450 3A4 were reduced on a high sodium diet. This study aimed to investigate the influence of high sodium diet on the pharmacokinetics and pharmacodynamics of fimasartan, which is a substrate of cytochrome P450 3A4 but not P-glycoprotein. The study design was a two-diet, two-period, two-sequence, randomized, open-label, and crossover with 1-week washout for diet. Eligible subjects were fed with either low sodium (50 mEq/day) diet or high sodium diet (300 mEq/day) for 7 days in the first hospitalization period and the other diet in the second period. On the seventh morning of each period, subjects received a single dose of fimasartan 60 mg in a fasted state. The serial plasma concentrations of fimasartan, serum aldosterone concentration (SAC), and plasma renin activity (PRA) were measured for pharmacokinetic-pharmacodynamic analysis. Sixteen subjects completed the study satisfying the compliance test for diets. Although the mean systemic exposure of fimasartan is slightly (≈10%) decreased on a high sodium diet, the difference was not statistically or clinically significant (P>0.05). The SAC and PRA after fimasartan administration were highly dependent on their baseline levels. The dietary sodium content influenced the baseline of SAC and PRA, but did not influence the ratio change of SAC and PRA after fimasartan treatment. The ratio change of SAC after fimasartan treatment was correlated to the systemic exposure of fimasartan (P<0.05), while the correlation between the ratio change of PRA after fimasartan treatment and the individual systemic exposure of fimasartan was not significant (P>0.05). In conclusion, the pharmacokinetics of fimasartan and ratio changes of SAC and PRA after fimasartan treatment were not significantly influenced by dietary sodium content.

COMPARATIVE BIOAVAILABILITY OF A FIXED-DOSE COMBINATION TABLET OF OLMESARTAN MEDOXOMIL/HYDROCHLOROTHIAZIDE IN HEALTHY KOREAN VOLUNTEERS.

Combination therapy with diuretics and angiotensin II type 1 (AT1) receptor antagonist is frequently recommended for the control of blood pressure in hypertensive patients. This study was targeted to compare pharmacokinetic profiles of a new generic fixed-dose combination (FDC) tablet of olmesartan medoxomil/hydrochlorothiazide 20/12.5 mg and a reference formulation of Olmetec Plus 20/12.5 mg tablets in healthy volunteers. The study design was a randomized sequence and two-way crossover study in healthy subjects. They were to be randomly assigned to either one of the two sequence groups; each subject sequentially received a single oral dose of reference and test tablet with 7-day washout period. Blood sample was collected at pre-dose and at 0.33, 0.67, 1, 1.33, 1.67, 2, 2.5, 3, 4, 6, 8, 12, 24, 36 and 48 h post-dose. The blood concentrations were analyzed by LC-MS/MS. Both of the 90% CI for the treatment ratios (test/reference) of C(max) and AUC(last) were to be in the range of 0.800-1.250 with regards to olmesartan medoxomil and hydrochlorothiazide; the geometric mean ratios (test/reference) for olmesartan C(max) and AUC(last) were 0.979 (90% CI, 0.934-1.027) and 0.992 (0.946-1.041), respectively, and those for hydrochlorothiazide C(max) and AUC(last) were 0.966 (0.975-1.110) and 0.999 (0.963-1.038), respectively. No serious adverse events were reported during the study. The generic formulation of olmesartan medoxomil/hydrochlorothiazide 20/12.5 mg tablet was bioequivalent with the reference formulation of Olmetec Plus 20/12.5 mg tablet in regards to the pharmacokinetic parameters of olmesartan medoxomil and hydrochlorothiazide. Clinical Research Information Service (CRIS) Registration Number: KCT0001025. (https://cris.nih.go.kr/ Mar 18, 2014)

Development and validation of a reliable and rapid LC-MS/MS method for simultaneous quantification of sacubitril and valsartan in rat plasma and its application to a pharmacokinetic study.

A selective, sensitive and rapid liquid chromatographic method with electrospray ionization tandem mass spectrometric detection has been developed and validated for simultaneous quantification of sacubitril and valsartan in rat plasma using telmisartan as internal standard (IS). The analytes were extracted by deprotenization of 50 µL of plasma sample using 200 µL of acetonitrile. In a short chromatographic run of 1.50 min run time, separation was achieved on a Hypersil Gold C18 column using a mobile phase composed of 0.1% formic acid in Milli-Q water-0.1% formic acid in acetonitrile in gradient elution mode. The quantification of target compounds was performed in a positive electrospray ionization mode and multiple reaction monitoring. Response was a linear function of concentration in the ranges of 0.5-20,000 ng/mL for both analytes, with r(2) > 0.9997. The intra- and inter-day precision and accuracy results were <15% and acceptable as per US Food and Drug Administration guidelines. Stability of compounds were established in a battery of stability studies, i.e. bench-top, autosampler and long-term storage stability as well as freeze-thaw cycles. The validated method can be used as a routine method to support pharmacokinetic studies. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of Age, Sex, and Race on the Safety and Pharmacokinetics of Single and Multiple Doses of Azilsartan Medoxomil in Healthy Subjects.

BACKGROUND AND OBJECTIVE: Azilsartan medoxomil (AZL-M) is an angiotensin II receptor blocker approved to treat hypertension. After oral dosing, AZL-M is quickly hydrolyzed to azilsartan (AZL). The aims of this study were to assess the effects of age, sex, and race on the pharmacokinetics of AZL-M in healthy subjects, as well as safety and tolerability. METHODS: Sixty-one healthy adults were enrolled in this phase I, single-blind, randomized placebo-controlled study (placebo control was for assessment of safety/tolerability only). Subjects were stratified by age (18-45 vs. 65-85 years), sex, and race (black vs. white) and given oral AZL-M 60 mg (3 × 20 mg capsules) or placebo as a single dose (Day 1) and consecutive daily doses (Days 4-8) (6:2 ratio for AZL-M:placebo per group). Pharmacokinetics were evaluated (AZL-M patients only) on Days 1-3 and 8-9 and safety/tolerability was monitored. RESULTS: Age, sex, and race had no clinically meaningful effect on AZL exposures after single or multiple dosing. Pharmacokinetic parameters remained similar between Days 1 and 8 for each age, sex, and race subgroup. The frequency of adverse events was similar for AZL-M (32%) and placebo (29%). No discontinuations or serious adverse events occurred. CONCLUSIONS: Based on these pharmacokinetic and safety/tolerability findings, no AZL-M dose adjustments are required based on age, sex, or race (black/white).

Population Pharmacokinetics and Exposure-Response of a Fixed-Dose Combination of Azilsartan Medoxomil and Chlorthalidone in Patients With Stage 2 Hypertension.

Population pharmacokinetic and exposure-response models for azilsartan medoxomil (AZL-M) and chlorthalidone (CLD) were developed using data from an 8-week placebo-controlled phase 3, factorial study of 20, 40, and 80 mg AZL-M every day (QD) and 12.5 and 25 mg CLD QD in fixed-dose combination (FDC) in subjects with moderate to severe essential hypertension. A 2-compartment model with first-order absorption and elimination was developed to describe pharmacokinetics. An Emax model for exposure-response analysis evaluated AZL-M/CLD effects on ambulatory systolic blood pressure (SBP). Estimated oral clearance and apparent volume of distribution (central compartment) were 1.47 L/h and 3.98 L for AZL, and 4.13 L/h and 62.1 L for CLD. Age as a covariate had the largest effect on AZL and CLD exposure (±20% change). Predicted maximal SBP responses (Emax ) were -15.6 and -23.9 mm Hg for AZL and CLD. Subgroup analysis identified statistically significant Emax differences for black vs nonblack subjects, whereby the reduced AZL response in black subjects was offset by greater response to CLD. The estimated Emax for AZL and CLD was generally greater in subjects with higher baseline BP. In conclusion, no dose adjustments to AZL-M or CLD are warranted based on identified covariates, and antihypertensive efficacy of AZL-M/CLD combination therapy is comparable in black and nonblack subjects.

Interactive Effect of the KCNJ11 Ile337Val Polymorphism and Cigarette Smoking on the Antihypertensive Response to Irbesartan in Chinese Hypertensive Patients.

OBJECTIVE: This study was designed to detect the association of the potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) gene polymorphism with antihypertensive therapeutic response to irbesartan in a large-scale Chinese hypertensive population. METHODS: A total of 1,099 patients with essential hypertension were enrolled to receive a daily dose of 150 mg irbesartan for 27 days. Pretreatment baseline blood pressure (BP) and posttreatment BP on the 28th day were measured. Plasma irbesartan concentrations were measured by high-performance liquid chromatography-fluorescence. The KCNJ11 I337V gene polymorphism was determined using high-throughput TaqMan technology. RESULTS: The HapMap data in the Han Chinese population showed that the I337V was used as a representative for 4 common functional polymorphisms. Our results showed that the association of antihypertensive response to irbesartan and the KCNJ11 genetic variant in the total sample was not significant. However, in nonsmokers, relative to the GG genotype, subjects with the homozygous AA genotype had a significantly higher therapeutic response to irbesartan (adjusted beta ± SE: 4.7±1.9 mm Hg, P = 0.015). In smokers, the subjects with the homozygous AA genotype had a significantly lower therapeutic response to irbesartan (adjusted beta ± SE: -5.6±2.5 mm Hg, P = 0.026). A multivariate linear regression model confirmed that there was a significant interactive effect between the KCNJ11 gene and smoking on irbesartan treatment (interaction P = 0.001). CONCLUSION: The interactive effect of smoking status and the KCNJ11 genotype may influence the antihypertensive effects of irbesartan, which indicates a consideration for future individualized antihypertensive drug treatment.

Alteration of the intravenous and oral pharmacokinetics of valsartan via the concurrent use of gemfibrozil in rats.

The present study aimed to examine the potential pharmacokinetic drug interaction between valsartan and gemfibrozil. Compared with the control given valsartan (10 mg/kg) alone, the concurrent use of gemfibrozil (10 mg/kg) significantly (p < 0.05) increased the oral exposure of valsartan in rats. In the presence of gemfibrozil, the Cmax and AUC of oral valsartan increased by 1.7- and 2.5-fold, respectively. Consequently, the oral bioavailability of valsartan was significantly higher (p < 0.05) in the presence of gemfibrozil compared with that of the control group. Furthermore, the intravenous pharmacokinetics of valsartan (1 mg/kg) was also altered by pretreatment with oral gemfibrozil (10 mg/kg). The plasma clearance of valsartan was decreased by two-fold in the presence of gemfibrozil, while the plasma half-life was not altered. In contrast, both the oral and intravenous pharmacokinetics of gemfibrozil were not affected by the concurrent use of valsartan. The cellular uptake of valsartan and gemfibrozil was also investigated by using cells overexpressing OATP1B1 or OATP1B3. Gemfibrozil and gemfibrozil 1-O-ß glucuronide inhibited the cellular uptake of valsartan with IC50 values (µm) of 39.3 and 20.4, respectively, in MDCK/OATP1B1, while they were less interactive with OATP1B3. The cellular uptake of gemfibrozil was not affected by co-incubation with valsartan in both cells. Taken together, the present study suggests the potential drug interaction between valsartan and gemfibrozil, at least in part, via the OATP1B1-mediated transport pathways during hepatic uptake. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Development, validation and application of the liquid chromatography tandem mass spectrometry method for simultaneous quantification of azilsartan medoxomil (TAK-491), azilsartan (TAK-536), and its 2 metabolites in human plasma.

Azilsartan medoxomil potassium salt (TAK-491) is an orally administered angiotensin II type 1 receptor blocker for the treatment of hypertension and is an ester-based prodrug that is rapidly hydrolyzed to the pharmacologically active moiety, azilsartan (TAK-536), during absorption. TAK-536 is biotransformed to the 2 metabolites M-I by decarboxylation and M-II by dealkylation. In this study, we developed and validated a LC/MS/MS method which can simultaneously determine 4 analytes, TAK-491, TAK-536, M-I and M-II. The bioanalytical method can be outlined as follows: two structural analogues are used as the internal standards. The analytes and the IS are extracted from human plasma using solid phase extraction. After evaporating, the residue is reconstituted and injected into a LC/MS/MS system with an ESI probe and analyzed in the positive ion mode. Separation is performed through a conventional reversed-phase column with a mobile phase of water/acetonitrile/acetic acid (40:60:0.05, v/v/v) mixture at a flow rate of 0.2mL/min. The total run time is 8.5min. The calibration range is 1-2500ng/mL in human plasma for all the analytes. Instability issues of the prodrug, TAK-491, were overcome and all the validation results met the acceptance criteria in accordance with the regulatory guideline/guidance. As a result of the clinical study, the human PK profiles of TAK-536, M-I and M-II were successfully obtained and also it was confirmed that TAK-491 was below the LLOQ (1ng/mL) in the human plasma samples.

Mixed amlodipine/valsartan overdose treated by the molecular adsorbent recirculating system (MARS™).

CASE REPORT: We describe the case of a 58-year-old woman who developed a severe distributive shock following the intentional ingestion of a large overdose of amlodipine (480 mg) combined with valsartan (3680 mg). Extreme vasoplegia remained refractory to maximal standard therapy including fluid resuscitation, intravenous calcium, vasopressors at very high doses, hyperinsulinemia-euglycemia therapy, lipid emulsion, and methylene blue administration. Besides, the patient exhibited hyperglycemia refractory to very high doses of insulin. Due to its theoretical ability to effectively remove protein-bound drugs such as amlodipine from the circulation, albumin dialysis with the molecular adsorbent recirculating system (MARS™) was performed during two consecutive sessions. Blood was drawn for toxicokinetic calculations. Amlodipine elimination half-life during the first MARS™ session was calculated at 7.6 h. In addition, there was a rapid fall in blood glucose, requiring the introduction of a continuous infusion of glucose in order to achieve euglycemia. Moreover, a few hours after the initiation of the MARS™ therapy, the hemodynamic status was not significantly modified but a significant tapering of epinephrine infusion was possible, together with a progressive decrease of blood lactate level. However, the need for vasopressors in decreasing doses was present until day 5 post-ingestion. Eventually, the patient fully recovered and was discharged home 8 days after admission. DISCUSSION: The role of the MARS™ in the treatment of severe poisoning of calcium channel blockers is still to be defined. We were able to demonstrate a relatively short elimination half-life of amlodipine. A decreased insulin resistance and a reduction of epinephrine infusion were also observed.