The pathophysiology of recurrent postprandial heartburn and the basis for the effectiveness of antacids or low doses of histamine H2-receptor antagonists have not been well studied.
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 ingestion of a meal over 0.5 h. Heartburn severity was assessed at 15-min intervals beginning at the end of the meal. Each subject randomly received placebo, 75 mg ranitidine, 420 mg calcium carbonate, and ranitidine plus calcium carbonate. Values for pH were converted to acid concentration (mM) and integrated acidity was calculated from the cumulative, time-weighted means of the acid concentrations for every second of the postprandial recording period.
There was a close temporal relationship between heartburn and oesophageal acidity. Most oesophageal acid exposure occurred over a 90-min period that began approximately 45 min after the end of the meal. During this period the gastric acid concentration was less than 5% of maximal. Ranitidine significantly decreased gastric but not oesophageal acidity, whilst antacid 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.
Determining integrated gastric and oesophageal acidity provides novel information regarding the pathophysiology of meal-induced heartburn as well as the actions of low-dose ranitidine and antacid. For subjects with meal-induced heartburn, treatment with low-dose ranitidine plus antacid is particularly effective in decreasing gastric and oesophageal acidity as well as heartburn severity.