The effects of roxatidine acetate on 24-hour intragastric acidity. Investigations in healthy volunteers and comparison with ranitidine and placebo.

In a series of double-blind randomised studies in normal volunteers with continuous intragastric pH monitoring, the effects of different dosage regimens of roxatidine acetate, a new H2-receptor antagonist, were compared with placebo and ranitidine. Roxatidine acetate 75 mg twice daily decreased median 24-hour gastric acidity from pH 1.6 to 3.2 and median nocturnal acidity from 1.5 to 3.0. Roxatidine acetate 150 mg at bedtime raised median 24-hour pH in the same 17 subjects to 2.4 and nocturnal pH to 5.9. In the second experiment, in 14 volunteers, roxatidine acetate 150 mg at bedtime was as effective as ranitidine 300 mg at night, raising median nocturnal pH from 1.4 to 6.65 compared to 6.7 for ranitidine. However, when drugs were taken after the evening meal (post cenam nocte; PCN) roxatidine acetate 150 mg was less potent than ranitidine 300 mg, with median night-time pH rising from 1.3 to 3.2 and 4.0, respectively, in 28 volunteers. Roxatidine acetate 300 mg PCN produced the greatest rise of pH, to 4.9, suggesting that the true potency ratio of the 2 drugs is between 1 and 2.