Reduction of postprandial gastric acidity and pepsin concentration by ranitidine and antacids in healthy volunteers.

Small aliquots of gastric content were withdrawn every tenth minute for 7 h in 11 healthy volunteers with a maximal gastric acid output of more than 20 mmol h-1. After 20 min a steak meal was given. Ranitidine hydrochloride 100 mg administered with the meal increased postprandial gastric pH and reduced acid concentration markedly throughout the test. Two tablets of antacids with a neutralizing capacity of approximately 20 mmol per tablet 1 and 3 h after the meal reduced gastric acidity significantly less than ranitidine and did not prevent an increase in acidity to control level during the interval between the two doses. In the control experiments 40% of the pH readings during the 4 postprandial hours were at or above the pre-prandial pH levels. Antacids and ranitidine increased this to 85% and 96% respectively. Antacids had no effect after the fourth postprandial hour, had very little effect when given in addition to ranitidine, but reduced the mean four hour postprandial pepsin concentration more than ranitidine.