A study was designed to assess gastric pH in healthy individuals and determine the value of different definitions of onset of action of ranitidine and famotidine when treatment is given after a meal.

Investigators assessed intragastric pH when placebo, ranitidine 150 mg, ranitidine 75 mg or famotidine 10 mg was given 30 min following a meal. Twenty four healthy individuals were included in the study.

• On defining onset of action as the earliest time when mean gastric pH was statistically significantly higher (P < 0.05) with treatment compared to the corresponding value with placebo, the onset of action of ranitidine 75 mg and 150 mg was 55 min, and that of famotidine 10 mg was 90 min.
• When investigators defined onset of action in terms of a particular reduction in gastric acid concentration for the whole group or for individual participants, a variation in the relative times of onset was noted for ranitidine 75 mg and famotidine 10mg.

 Ranitidine has faster onset of action compared to famotidine

Source: Gardner JD, Ciociola AA, Robinson M, Mcisaac RL. Determination of the time of onset of action of ranitidine and famotidine on intra-gastric acidity. Aliment Pharmacol Ther. 2002;16(7):1317-26.