Population pharmacokinetics of omeprazole in a random Iranian population

Omeprazole is metabolized predominantly by CYP2C19, a polymorphically expressed enzymes that show marked interindividual and interethnic variation. These variations cause a substantial differences that have been reported in the pharmacokinetics of omeprazole. The aim of the present study was to evaluate the pharmacokinetic parameters of omeprazole in a random Iranian population. From the 20 subjects, only 17 healthy unrelated individuals of either sex (9 females age range 22-24 years) participated in the study. After an overnight fasting, a sample of blood was collected. The subjects received a single oral dose of 40 mg capsule of omeprazole (losec) and blood samples were taken up to 8 hours. Omeprazole was analyzed by the HPLC method and population pharmacokinetic analysis was performed using population pharmacokinetic modelling software P-Pharm. The mean value for apparent plasma clearance (CL/F) was 20.8±6.9 (L.h-1). The corresponding value for apparent volume of distribution (V/F), and t1/2 beta were 21.6±7.5 (L) and 0.8±0.3 (h), respectively. A comparison of the weight normalized V/F and CL/F of omeprazole between males and females revealed that both parameters were significantly higher in females than males (p?0.03). These results show a substantial interindividual variability in omeprazole pharmacokinetics and this might affect the therapeutic effects of omeprazole as reported previously.