Evaluation of antacid tablets and liquid in fasting and fed men and women

In view of in vitro tests suggesting good performance of an experimental tablet formulation of an aluminum hydroxide-magnesium hydroxide antacid, a study was conducted to evaluate the efficacy in vivo. Twenty-three healthy men and women were enrolled in the study, which was carried out in two parts: fasting and postprandial. Eight of the volunteers failed to qualify because of repeated baseline pH greater than 2.5. In the 15 participants who qualified, the intragastric pH was monitored for up to 240 minutes after the administration of one or two experimental tablets, 5 or 10 ml of a commercially available liquid antacid, or placebo. In the fasting subjects (n = 10), the antacids rapidly increased the mean pH. One antacid tablet and 5 ml of liquid antacid yielded similar results, with mean peak pH values of 5.2 and 4.8 and durations above pH 3.5 of 25 and 40 minutes, respectively. When the doses were doubled, 10 ml of liquid produced a peak pH of 6.7 and maintained the pH above 3.5 for 40 minutes, whereas two tablets produced a peak pH of 4.8 and maintained pH above 3.5 for 15 minutes. In the fed subjects (n = 10), neither antacid formulation at either dose significantly raised intragastric pH. Further studies are needed to establish the optimal time for postprandial administration of antacids.