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Modeling of the pharmacokinetic/pharmacodynamic interaction between irbesartan and hydrochlorothiazide in normotensive subjects
Author(s) -
Hedaya Mohsen A.,
Helmy Sally A.
Publication year - 2015
Publication title -
biopharmaceutics and drug disposition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.419
H-Index - 58
eISSN - 1099-081X
pISSN - 0142-2782
DOI - 10.1002/bdd.1935
Subject(s) - irbesartan , hydrochlorothiazide , blood pressure , pharmacology , pharmacodynamics , pharmacokinetics , medicine , endocrinology
Purpose To investigate the pharmacokinetic/pharmacodynamic (PK/PD) interaction between irbesartan (IRB) and hydrochlorothiazide (HCT) in normotensive subjects. Methods A three‐way crossover study was used. Serial drug concentrations and drug effects, including systolic and diastolic blood pressure and heart rate were monitored after administration of irbesartan and hydrochlorothiazide alone and in combination. The data were fitted to a PK/PD model and the parameters for irbesartan and hydrochlorothiazide when administered alone and in combination were compared. Results The plasma profiles for irbesartan and hydrochlorothiazide followed the two‐compartment model after a single dose. The PK parameters of irbesartan were not affected by hydrochlorothiazide; however irbesartan decreased the hydrochlorothiazide AUC by 25% and increased its clearance by 25%. There were no significant changes in heart rate after each drug alone or in combination. Irbesartan plus hydrochlorothiazide had a greater blood pressure lowering effect compared with irbesartan alone, despite the unchanged irbesartan PK. The relationship between irbesartan plasma concentration and its effects plotted in chronological order showed anticlockwise hysteresis. The PD parameter estimates for the effect of irbesartan on systolic blood pressure, when administered with hydrochlorothiazide were significantly different from those when irbesartan was administered alone. This was manifested by a 25% increase in E max , and a 40% decrease in EC 50 , suggesting a synergistic blood pressure lowering effect for the combination. While parameter estimates for the effect of irbesartan on diastolic blood pressure were changed by hydrochlorothiazide, the differences were only significant for EC 50 . Conclusion A limited potential for clinically significant interactions between irbesartan and hydrochlorothiazide at the given doses were observed; therefore, no dosage adjustments were recommended for either drug when used together. ( ClinicalTrials.gov Identifier NCT01858610) Copyright © 2014 John Wiley & Sons, Ltd.