Synergy between low-dose ranitidine and antacid in decreasing gastric and oesophageal acidity and relieving meal-induced heartburn

Background: The pathophysiology of recurrent postprandial heartburn and the basis for the effectiveness of antacids or low doses of histamine H-2-rece ptor antagonists have not been well studied. Methods: The selected subjects (n = 26) had heartburn more than four times a week for at least 2 months, which was responsive to antacids. Gastric pH and oesophageal pH were measured for 1 h before, during, and 4.5 h after in gestion of a meal over 0.5 h. Heartburn severity was assessed at 15-min int ervals beginning at the end of the meal. Each subject randomly received pla cebo, 75 mg ranitidine, 420 mg calcium carbonate, and ranitidine plus calci um carbonate. Values for pH were converted to acid concentration (mM) and i ntegrated acidity was calculated from the cumulative, time-weighted means o f the acid concentrations for every second of the postprandial recording pe riod. Results: There was a close temporal relationship between heartburn and oeso phageal acidity. Most oesophageal acid exposure occurred over a 90-min peri od that began approximately 45 min after the end of the meal. During this p eriod the gastric acid concentration was less than 5% of maximal. Ranitidin e significantly decreased gastric but not oesophageal acidity, whilst antac id significantly decreased oesophageal but not gastric acidity. Ranitidine plus antacid significantly decreased both gastric and oesophageal acidity. Antacid alone and ranitidine plus antacid significantly decreased heartburn severity. Conclusions: Determining integrated gastric and oesophageal acidity provide s novel information regarding the pathophysiology of meal-induced heartburn as well as the actions of low-dose ranitidine and antacid. For subjects wi th meal-induced heartburn, treatment with low-dose ranitidine plus antacid is particularly effective in decreasing gastric and oesophageal. acidity as well as heartburn severity.