The effect of sodium bicarbonate versus aluminum-magnesium hydroxide on postprandial gastric acid in duodenal ulcer patients.

When ingested 1 hour after a meal, conventional liquid antacids have a buffering effect of approximately 2 hours, while in the fasting state their effect is brief, lasting less than 1 hour. We tested the hypothesis that equal doses of antacid, one water soluble (sodium bicarbonate) and the other water insoluble (aluminum hydroxide plus magnesium hydroxide, MaaloxR), would have similar durations of postprandial buffering if the water soluble antacid regenerates the particulate protein buffer of the meal that leaves the stomach more slowly than liquids. Tests were conducted in random order on three separate days in 10 patients with duodenal ulcer. The effects of 30 ml of 2.39 M sodium bicarbonate (6.17 g, about 1 teaspoonful), the aluminum-magnesium antacid, each equivalent to 71.7 mmol of in vitro buffer, and water as a control on pH, hydrogen ion activity, and titratable acidity were compared. Thirty milliliters of each was swallowed 1 and 3 hours after ingestion of a standard solid plus liquid. Compared to the water control each dose of sodium bicarbonate significantly increased intragastric pH and decreased hydrogen ion activity and titratable acidity for only 1 hour. Each dose of the aluminum-magnesium antacid significantly buffered intragastric contents for 2 hours. These findings indicate that sodium bicarbonate transiently buffers postprandial intragastric contents. Therefore, sodium bicarbonate fails to reconstitute the protein buffer of the meal effectively, and the observations suggest that it leaves the stomach rapidly with the liquid phase of the meal. However, the water insoluble, aluminum-magnesium antacid has a longer duration of buffering, probably because it leaves the stomach more slowly, largely with the solid portion of the meal.