[The effect of ranitidine on gastric pH measured by continuous monitoring over 24 hours in healthy subjects. Comparison of 2 methods of administration: 150 mg morning and night, vs 300 mg in a single dose at night].

The gastric pH of 8 healthy subjects was determined, in a continuous fashion, during three different 24 hour periods corresponding to the 3 following treatments: Placebo, ranitidine 150 mg twice per day, and ranitidine 300 mg in the evening. During each period, the feeding conditions were normal and standardized. The results are expressed in terms of the number of hours under a threshold pH value. In comparison with the placebo, ranitidine, regardless of its mode of administration, results in a significant decrease of the mean number of hours under pH 1.5, 2 and 3 during 24 hours; no significant difference was demonstrated between the two modes of administration in 24 hours. During the 12 night-hours, a single dose of 300 mg of ranitidine was more effective to ranitidine taken in 2 doses for pH thresholds of 2 and 3, while during the 12 day-hours, no difference was demonstrated for pH thresholds of 1.5, 2 and 3. The analysis of the mean pH graphs in relation to time, suggests that a single 300 mg dose is more effective than the same dose divided into 2 doses during the day. These results tally with the variations of ranitidine plasma levels in 24 hours. These results justify, from a pharmacological standpoint, the prescription of a single dose of ranitidine, in the evening.