Stereoselective interaction of tolvaptan with amiodarone under racemic metabolic impact by CYP3A5 genotypes in heart failure patients.

PURPOSE: The diuretic effect of tolvaptan is largely blood level-dependent although it does exhibit interindividual differences according to cytochrome P450 (CYP) 3A5 genotype. This study aimed to investigate the pharmacokinetic relationship between plasma tolvaptan and its monohydroxylate enantiomers and the factors affecting their metabolism in heart failure patients. METHODS: Japanese heart failure patients (n = 88) receiving oral tolvaptan (median dosage 7.5 mg/day) were enrolled. Blood samples were collected prior to the dosing on day 6 or later after first administration to determine the plasma concentrations of tolvaptan and its monohydroxylate enantiomers. Gene polymorphisms of CYP3A5, carbonyl reductase (CBR) 1/3, and ATP-binding cassette subfamily B member (ABCB) 1 were analyzed for their impact on tolvaptan pharmacokinetics. Serum laboratory test values and concomitant use of amiodarone were evaluated as factors related to tolvaptan metabolism. RESULTS: The median of the sum of the 5S- and 5R-tolvaptan plasma concentrations was 48.9 (range, 15.3-100) ng/mL. CYP3A5 genotypes significantly affected the concentration ratio of all enantiomeric metabolites to tolvaptan, while the other metabolic-related gene polymorphisms had no influence. A negative correlation was found between serum albumin and the enantiomeric ratio of tolvaptan and monohydroxylate DM-4111. Concomitant use of amiodarone increased the plasma levels of whole tolvaptan but significantly decreased the metabolic ratios of 5R-tolvaptan. 5S-tolvaptan was selectively synthesized from ketone MOP-21826 by CBR1 with a substantially smaller reaction velocity compared to tolvaptan monohydroxylation by CYP3A4/5. CONCLUSION: This study clarified the racemic impact of CYP3A5 genotypes on tolvaptan metabolism. Amiodarone may stereoselectively interact with R-forms rather than S-forms of tolvaptan.

Simple LC-MS/MS method using core-shell ODS microparticles for the simultaneous quantitation of edoxaban and its major metabolites in human plasma.

Edoxaban is mainly enzymatically converted to a 4-carboxylic acid form (4CA-EDX) and an N-desmethyl form (ND-EDX) in humans. This study aimed to establish a simple liquid chromatography-tandem mass spectrometry method using core-shell octadecyl silica (ODS) microparticles for the simultaneous quantitation of edoxaban and its two major metabolites in human plasma. Analytes extracted from plasma specimens by a one-step deproteinization were separated using a 2.6-µm core-shell ODS microparticulate column and linear acetonitrile-ammonium acetate gradient elution at a flow rate of 0.25 mL/min with a run time of 7 min. The mass spectrometer was operated in the positive ion multiple reaction monitoring mode. Plasma samples collected from 20 patients with atrial fibrillation were analyzed by the present method. The chromatograms of drug-free human plasma had no interfering peaks. The calibration curves of edoxaban, 4CA-EDX, and ND-EDX were linear over the concentration ranges of 1.25-160, 0.47-60, and 0.12-15 ng/mL, respectively. Their pretreatment recoveries and matrix factors were 88.7-109.0% and 87.0-101.6%, respectively. The intra- and inter-day accuracy and imprecision values were 85.9-112.8% and within 13.3%, respectively. The plasma concentrations of edoxaban, 4CA-EDX, and ND-EDX in the patients had ranges of 17.8-102, 1.67-25.7, and 0.685-5.34 ng/mL, respectively. All the analytes were measurable within their calibration curves. In conclusion, this validated method for the simultaneous determination of edoxaban and its major metabolites was successfully applied to plasma specimens obtained from patients with atrial fibrillation.

An enantiomeric quantitative LC-MS/MS method for tolvaptan and its monohydroxylates in human plasma using a reversed-phase separation procedure.

Racemic tolvaptan possessing an asymmetric carbon is metabolized to three pairs of monohydroxylate enantiomers of diol form with V2 receptor antagonistic activity via CYP3A. This study aimed to develop a simultaneous quantitative liquid chromatography-tandem mass spectrometry method for 5R- and 5S-tolvaptan and their monohydroxylate enantiomers in human plasma and to apply it to patient samples. Deproteinized plasma specimens were separated using a polysaccharide derivative chiral column in a reversed-phase elution mode. The mass spectrometer was run in positive ion electrospray ionization mode. The chromatographic peaks of tolvaptan monohydroxylate enantiomers were identified by the recombinant CYP3A4/5 digestion of 5R- and 5S-tolvaptan. The calibration curves ranged over the plasma concentrations of 0.25-125 ng/mL for 5R- and 5S-tolvaptan, 0.025-12.5 ng/mL for 4R5R- and 4S5S-diols, and 0.025-38.15 ng/mL for 4S5R-, 4R5S-, 3S5R-, and 3R5S-diols with a large variation. Their pre-treatment recovery rates and matrix factors in human plasma were 85.2-112.9 % and 86.9-113.1 %, respectively. The intra- and inter-day accuracy and imprecision were 92.3-113.8 % and 3.5-14.6 % for all analytes, respectively. The plasma concentration ranges of 5R- and 5S-tolvaptan, 4R5R-, 4S5S-, 4S5R-, 4R5S-, 3S5R-, and 3R5S-diols in heart failure patients with a 5-fold dilution procedure were 0.634-28.4, 2.37-131, 0.525-15.4, 0.0970-4.08, 6.82-108, 0.271-6.49, 0.394-4.18, and 4.81-39.8 ng/mL, respectively. In conclusion, the present method has an acceptable analytical performance level and can be helpful for characterization of the plasma 5R- and 5S-tolvaptan and their monohydroxylate enantiomers in heart failure patients.

Impact of CYP3A5 genotype on tolvaptan pharmacokinetics and their relationships with endogenous markers of CYP3A activity and serum sodium level in heart failure patients.

Tolvaptan efficacy for heart failure has a large interindividual variation. This study aimed to evaluate the influence of CYP3A5 and ABCB1 genotypes on tolvaptan pharmacokinetics and their relationships with plasma markers of CYP3A activity and laboratory test values in heart failure patients. Fifty-eight heart failure patients receiving oral tolvaptan for volume overload were enrolled. Blood samples for determination of pre-dose plasma concentrations of tolvaptan and its metabolites were collected. CYP3A5 and ABCB1 genotypes, plasma 4ß-hydroxycholesterol/total cholesterol ratio (4ß-OHC/TC) and 25-hydroxyvitamin D (25-OHD), and serum laboratory test values were evaluated. The CYP3A5*3/*3 genotype was associated with a higher plasma concentration of tolvaptan but not with its metabolic ratios. The ABCB1 3435C > T, 2677G > T/A and 1236C > T polymorphisms affected neither tolvaptan pharmacokinetics nor its metabolism. Plasma 4ß-OHC/TC and 25-OHD concentration were not correlated with plasma tolvaptan concentration. In a stratified analysis based on CYP3A5 genotype, plasma 4ß-OHC/TC had a negative correlation with plasma tolvaptan concentration in the patients with the CYP3A5*1 allele, while the plasma concentration of 25-OHD did not. The CYP3A5*3/*3 genotype was associated with a higher serum sodium level in the patients with volume overload. The plasma concentration of 25-OHD had a positive correlation with the serum total bilirubin level. In conclusion, CYP3A5*3 but not ABCB1 genotypes elevated tolvaptan plasma exposure in heart failure patients. CYP3A5-deficient patients treated with tolvaptan had a higher serum sodium level. The CYP3A5 genotype altered the relationship between plasma tolvaptan and 4ß-OHC.

Validated liquid chromatography coupled to tandem mass spectrometry method for simultaneous quantitation of tolvaptan and its five major metabolites in human plasma.

BACKGROUND: Tolvaptan is converted to major metabolites including three monohydroxylates (DM-4110, DM-4111 and DM-4119), an oxidate (MOP-21826) and a carboxylate (DM-4103) in humans. This study developed a simultaneous quantitative method for tolvaptan and its five major metabolites in human plasma using liquid chromatography coupled to tandem mass spectrometry. METHODS: Deproteinized plasma specimens using acetonitrile were separated using a 3- µm particle size octadecylsilyl column with 250 mm length and a simple linear gradient program at a flow rate of 0.3 mL/min with a total run time of 15 min. This method was applied to the determination of plasma samples collected from 20 heart failure patients treated with 3.75-15 mg tolvaptan. RESULTS: No interfering peak was found in drug-free plasma specimens. The calibration curves of tolvaptan, DM-4110, DM-4111, DM-4119, MOP-21826 and DM-4103 were linear over the concentration ranges of 3.125-1000, 0.3125-100, 1.25-400, 0.625-200, 0.125-40 and 31.25-10,000 ng/mL, respectively. Their pretreatment recovery rates and matrix factors were 94.1-113.9% and 86.9-108.0%, respectively. The intra- and inter-day accuracies and imprecisions were 91.6-106.5% and 0.9-10.9%, respectively, for all analytes. The plasma concentration ranges of tolvaptan, DM-4110, DM-4111, DM-4119, MOP-21826 and DM-4103 were 9.37-280, 1.91-16.3, 3.43-88.9, 1.43-10.4, 0.160-1.01 and 40.2-1471 ng/mL, respectively, in heart failure patients. CONCLUSIONS: This validated method with acceptable analytical performance can be utilized for evaluating the pharmacokinetics of oral tolvaptan, including the determination of its major metabolites, in heart failure patients.