A study by Berstad and colleagues assessed the effect of ranitidine and antacids on reduction of postprandial gastric acidity in healthy individuals.

Investigators obtained small aliquots of gastric content after every 10^th minute for 7 hours in 11 healthy volunteers having a maximal gastric acid output of over 20 mmol/h. A steak meal was given after 20 minutes.

• Ranitidine 100 mg was administered with the meal. It led to a considerable increase in postprandial gastric pH and a reduction in acid concentration throughout the test.
• Two tablets of antacids with a neutralizing capacity of about 20 mmol per tablet administered 1 and 3 h after the meal led to reduction in gastric acidity to a significantly lesser extent than ranitidine.
• The antacids did not prevent an increase in acidity to control level during the time period between the two doses.
• In control experiments, 40% of the pH readings over four postprandial hours were at or above the pH levels prior to meal. Antacids increased this to 85% while ranitidine raised this to 96%.
• Ranitidine lead to considerable increase in postprandial gastric pH and a reduction in acid concentration
• Antacids led to reduction in gastric acidity to a lesser extent than ranitidine.

Source: Berstad A, Rydning A, Kolstad B, Frislid K. Reduction of postprandial gastric acidity and pepsin concentration by ranitidine and antacids in healthy volunteers. Scand J Gastroenterol Suppl. 1981 Jun;69:67-73.