In Vivo and in Vitro Evaluation of Liquid Antacids

Abstract

An in vivo test of the efficacy of liquid antacids given after a meal was shown to yield reproducible results. An average dose-response curve, obtained with the use of various doses of a single antacid, was different in subjects whose peak histamine response exceeded 25 mEq per hour and in those whose response was less than 16.6 mEq per hour. In individual subjects, however, the peak histamine response did not accurately predict the in vivo reduction in gastric acidity by antacid. Although the relative in vivo potency of equal volumes of four different antacids varied widely, this potency could be predicted with reasonable accuracy by means of an in vitro test, which showed the potency per milliliter of antacid to vary 17-fold among different commercial products.

These experiments indicate that when antacids are prescribed, dosage should be determined by the milli-equivalents of neutralizing capacity rather than by an arbitrary volume or number of tablets of different antacids, that the variable responses of individual patients to antacids should be taken into account, and that the doses commonly used in the treatment of duodenal ulcer should be increased. (N Engl J Med 288:923–928, 1973)