Abstract
Two series of experiments have been performed in gastric fistula dogs to test the antisecretory effect of two different oral dosage forms of omeprazole: 2 μmol ± kg−1 ± day−1 as a methylcellulose suspension for 8 weeks and 0.5 μmol ± kg−1 ± day−1 in enteric-coated granules (ECG) for 3 weeks. There was an increasing inhibitory effect during the first days of repeated administration of omeprazole, which is in accordance with its long duration of action. The steady-state inhibitory level was reached after five doses. During the 8-week treatment with the omeprazole suspension (2 μmol ± kg−1) the mean maximal inhibitory level (3 h after dose) was 82%, and the mean minimal inhibitory level (24 h after dose) was 35%. With omeprazole in ECG (0.5 μmol ± kg−1) the steady-state maximal inhibition (4th h) was 60%, whereas 40% inhibition remained after 24 h. Thus, a more even inhibitory level over day and night seems to be obtained with the ECG formulation than with the suspension. Basal and food-stimulated plasma gastrin levels were not significantly affected by the treatment with 0.5 μmol ± kg−1, whereas food-stimulated gastrin levels were slightly increased during treatment with 2 μmol ± kg−1. Control levels of acid secretion were reached within 4 days of stopping treatment. In the present studies, in which the inhibition of acid secretion varied over 24 h between approximately 80% and 35% (maximum and minimum), no rebound effects could be detected as measured up to 1 month after cessation of treatment.