Calcium and acid rebound: a reappraisal.

We review acid rebound, the seemingly paradoxical increase in acid secretion resulting from administration of an antacid. Primarily a laboratory observation, the demonstration of the phenomenon was a major contributing factor to the swift, and possibly unjustified, fall from grace of calcium carbonate in the therapy of peptic ulcer disease despite years of apparently successful use. Calcium, as carbonate or other salts, causes an increase in gastric acid secretion owing, at least in part, to direct ionic stimulation. Another possible mode of action involves antral alkalinization with subsequent gastrin release. Other antacids, notably magnesium hydroxide and aluminum hydroxide, may therefore also cause rebound, but the data in this area are less convincing. Despite the demonstration that acid rebound occurs, no one has thoroughly investigated its clinical import. What limited data actually exist suggest no obvious clinically significant deleterious effect from use of calcium carbonate in peptic ulcer. Because of calcium carbonate's excellent acid-neutralizing capacity, its venerable past record in treating ulcer disease, and recent observations that low-dose antacids heal peptic ulcers, it is appropriate to reevaluate acid rebound, to focus on its clinical significance, if any.