Comparison of the effect of the antacid Rennie versus low-dose H2 -receptor antagonists (ranitidine, famotidine) on intragastric acidity

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Abstract
Symptoms of functional dyspepsia are common and patients often self-medicate with antacids, or with low-dose H2-antagonists which are available as over-the-counter medications. To date, there has been limited information available comparing the effects on intragastric acidity of these two types of over-the-counter medication. Therefore we studied the effect of the antacid Rennie and two H2-antagonists on the intragastric pH of fasting volunteers. Sixteen healthy, fasting volunteers were randomized into a double-blind, placebo-controlled, four-way crossover study comparing Rennie (calcium-magnesium carbonate) 1360 mg, ranitidine 75 mg, famotidine 10 mg and placebo. Their effect on gastric pH was monitored by a 4-h gastric pH-metry. The primary efficacy parameter was the time lag before an intragastric pH > 3.0 was reached after drug administration. The median time lag before pH > 3.0 was reached after drug administration was 5.8 min for Rennie, 64.9 min for ranitidine, 70.1 min for famotidine and 240.0 min for placebo. The percentage of time with values of pH > 3.0 was 10.4% for Rennie, 61.4% for ranitidine, 56.6% for famotidine and 1.4% for placebo. The onset of action in fasting volunteers was significantly faster with the antacid than with the two H2-antagonists. The duration of action was significantly longer with an H2-antagonist than with the antacid. This suggests that the two products should be used for different indications: antacids are superior for rapid pain relief, whereas H2-antagonists might be better for symptom prophylaxis—for example for nocturnal dyspepsia.