Comparison of gastric mucosal surface pH response times after intravenous administration of histamine2-receptor antagonists.

Gastric mucosal surface pH was measured endoscopically in patients with peptic ulcer, erosive gastritis, or nonulcer dyspepsia following intravenous administration of either 200-mg cimetidine, 50-mg ranitidine, or 40-mg famotidine. The mean baseline pH in the three treatment groups before drug administration ranged from 0.85 to 0.99, with no significant difference between groups. Following treatment with cimetidine, ranitidine, and famotidine, the mean response times for the mucosal surface pH values to increase to 3.5 were 10.1 +/- 5.9 minutes, 11.2 +/- 6.8 minutes, and 17.3 +/- 6.7 minutes, respectively. The corresponding response times to reach pH levels of 6.0 were 16.0 +/- 9.4 minutes, 17.0 +/- 5.4 minutes, and 31.2 +/- 21.7 minutes, respectively. The response times to pH levels of 3.5 and 6.0 were significantly faster in patients who received cimetidine compared with patients who received famotidine (P = 0.0088 to pH 3.5 and P = 0.046 to pH 6.0). The differences between cimetidine and ranitidine were not significant. These findings suggest that at recommended clinical doses, intravenous cimetidine provides rapid elevation of the gastric mucosal surface pH compared with other histamine2-receptor antagonists. This finding may be particularly relevant in the emergency care of patients with severe peptic ulcer disease (eg, patients with gastrointestinal hemorrhage).