Effect of Rennie Liquid versus Maalox Liquid on intragastric pH in a double-blind, randomized, placebo-controlled, triple cross-over study in healthy volunteers.

OBJECTIVES

Despite years of successful use of calcium-containing antacids in acid-related disease, allegations of gastric rebound following their intake has brought these agents into disrepute. By assessing intragastric acidity over the 24-h period, we evaluated whether antacids induce a clinically relevant acid rebound.

METHODS

Twelve healthy volunteers were assigned to a double-blind, placebo-controlled, triple cross-over comparison of placebo, Maalox Liquid, and a calcium-containing antacid, Rennie Liquid. The two antacids had identical neutralizing capacity. Each drug was administered at standard doses q.i.d 1 h after the main meals (at 1000, 1400, and 1900 h) and at bedtime (2300 h). Intragastric acidity was monitored by continuous ambulatory 24-h pH-metry on 3 separate days with a wash-out period of 1 wk. Special attention was given to the acidity of pre-determined postantacid time intervals during the day and night.

RESULTS

Both antacids led to a significant increase of the median 24-h pH and the median pH of the first postantacid hour, compared with placebo. Neither Rennie Liquid nor Maalox Liquid led to a drop of intragastric pH during the putative acid rebound time (2nd and 3rd postantacid hr and at night). A marginal increase in serum calcium and gastrin concentration with Rennie Liquid, and magnesium concentration with Maalox Liquid, were observed.

CONCLUSIONS

No gastric acid rebound was detected with the calcium carbonate-containing antacid, Rennie Liquid, or with Maalox Liquid at standard doses. An identical increase of intragastric pH was achieved with Rennie Liquid and Maalox Liquid during the first postantacid hour and the entire 24-h period.