Renal clearance and urinary excretion of omeprazole in healthy female volunteers in Pakistan

Omeprazole is a widely prescribed proton pump inhibitor to treat various gastric acid hyper secretion disorders. The present study was designed to evaluate the renal clearance and urinary excretion of omeprazole in eight healthy female volunteers to increase the understanding of the contributing factors such as demographics variability in the renal clearance and urinary excretion of omeprazole under indigenous conditions. The urine and blood samples were collected 0.5, 1, 1.5, 2, 3, 4, 6, 8 hours after oral administration of enteric coated omeprazole (20 mg) and drug concentration in the samples was determined by High Performance Liquid Chromatography (HPLC) with C-18 column and UV detector. Urinary excretion and renal clearance of omeprazole was calculated and data was statistically analyzed by using regression/correlation technique. Endogenous creatinine was also measured by reagent kit available in the market. The results indicate that mean diuresis was 0.0172 +/- 0.0029 ml/min/kg. While the mean values of renal clearance of creatinine and omeprazole were 1.315 +/- 0.103 and 0.66 +/- 0.0042 ml/min. kg, respectively. Whereas, clearance ratio was 0.055 +/- 0.007 which indicates back diffusion. The cumulative percentage of dose excreted was 6.71 +/- 0.358. A significant (p<0.05) negative correlation (r= -0.457) between clearance ratio and urine pH of omeprazole reflecting glomerular filtration reabsorption of drug at kidney tubular level while significant (p<0.05) negative correlation (r= -0.681) between clearance ratio and plasma concentration of omeprazole indicates the involvement of active tubular secretion of drug. It can be concluded that during glomerular filtration, omeprazole diffuse back/reabsorption. Therefore, Urinary excretion of omeprazole in indigenous healthy female subjects was observed to be lower than given in the literature values.