The comparative efficacy of cimetidine and ranitidine in controlling gastric pH in critically ill patients.

The comparative efficacy of intravenous cimetidine and ranitidine in controlling gastric pH in 100 intensive care unit patients was assessed in a double blind, prospective, randomized study. The total number of gastric pH determinations and the number of pH determinations with pH less than five were recorded. Patients received either cimetidine or ranitidine via continuous infusion, with dosage adjustments for patients with renal insufficiency. Antacids were administered each time the gastric pH was less than five. There was no difference overall in the number of patients who had at least one gastric pH determination less than pH 5. There was however, a larger proportion of patients with greater than or equal to 10, greater than or equal to 15, greater than or equal to 20 and greater than or equal to 25 per cent of gastric pH determination less than pH 5 in the cimetidine group than in the ranitidine group. This difference was statistically significant for greater than or equal to 25 per cent. The drugs were well tolerated. Ranitidine was as effective as cimetidine and possibly more so in controlling gastric pH.