The effect of oral omeprazole on pentagastrin stimulated gastric acid secretion was studied in 11 healthy subjects. Doses of 20-80 mg produced dose dependent inhibition of acid secretion, with total suppression at the highest dose. Omeprazole was absorbed and eliminated from plasma rapidly and the inhibitory effect was related to the area under the plasma concentration time curve. The duration of action was long and single doses of 20 and 40 mg reduced acid secretion significantly for one and three days, respectively. Omeprazole in a dose of 15 mg given once daily for five days, suppressed acid secretion continuously, the inhibitory effect stabilising after three days at a predose inhibition of about 30% and a postdose inhibition of about 80%.

Effect of omeprazole--a gastric proton pump inhibitor--on pentagastrin stimulated acid secretion in man.