Night-time or morning dosing with H2-receptor antagonists: studies on acid inhibition in normal subjects

H2-receptor antagonists are conventionally given at night. However, it remains unproven whether this regimen affords superior acid inhibition or healing rates for patients with duodenal ulcers compared to morning dosing. We have therefore examined the acid inhibitory effect of 300 mg ranitidine at night compared to 300 mg ranitidine in the morning in 8 normal male subjects. Intragastric acidity was measured by the radiotelemetry method and acid inhibition calculated from the percentage decrease in the area under the curve for hydrogen ion activity against time. Night-time ranitidine resulted in a significantly better (P less than 0.02) decrease of intragastric acidity than the same dose given in the morning (66.8 (61.8-77.6)% vs. 34 (15.5-49.1)%). This difference was found to be due to the fact that morning ranitidine inhibited gastric acid secretion when the intragastric acidity was already buffered by food. These data support the superiority of nocturnal dosing with H2-antagonists.