Abstract
We have studied the relationship between reduction of gastric acid secretion and fasting plasma gastrin concentrations during once daily omeprazole treatment. Healthy subjects were given omeprazole for 5 days in daily doses of 5, 10, 20, 40, or 80 mg. Acid secretion and fasting gastrin concentration were measured 6 h (maximal omeprazole effect) and 24 h (minimal omeprazole effect) after the fifth omeprazole dose. Omeprazole in doses lower than 20 mg daily did not suppress pentagastrin-stimulated acid secretion in all subjects 6 h after dosing on the 5th day. Doses of 20–80 mg omeprazole, however, significantly reduced acid secretion 24 h after the fifth dose, the range being 36–76%. A relationship between degree of acid inhibition and fasting gastrin concentration was observed. However, acid secretion needed to be reduced by more than 80% before gastrin levels were clearly affected. This degree of acid inhibition was only achieved 6 h after administration of omeprazole in doses of 20 mg and higher. The inhibitory effect of omeprazole on acid secretion decreased 24 h after dosing. Thus, fasting gastrin concentrations were moderately increased in the beginning and normalized at the end of each 24-h period during treatment with daily doses of 20–80 mg omeprazole.