Efficacy of ranitidine in olanzapine-induced weight gain: a dose-response study

Weight gain has long been recognized as a side-effect of atypical antipsychotic drugs. Numerous new approaches have been tried for prevention of weight gain, the H2 blockers being one of them. The study was conducted with the aim to evaluate the efficacy of ranitidine in olanzapine-induced weight gain at two fixed doses of 150 and 300 mg day^-1 .

Seventy-five inpatients with an ICD-10-DCR diagnosis of schizophrenia as their first episode were randomized into three groups of 25 patients each, receiving 150 mg day^-1 ranitidine, 300 mg day^-1 ranitidine and third group receiving only olanzapine. Their weight and body mass index (BMI) were measured at baseline and at intervals of 4 and 8 weeks.

All patients were comparable with respect to their weight and BMI at baseline. When a change in the weight and BMI was assessed at 4 and 8 weeks from baseline, no significant difference was observed between the three groups.

Ranitidine at doses of 150 and 300 mg day^-1 when combined with olanzapine was ineffective in attenuating olanzapine-induced weight gain. The likely reasons could be the use of low doses for a shorter period of time, or mechanisms other than H2 receptors might play an important role in weight gain.