Differential effect of clozapine on weight: a controlled study

OBJECTIVE: This study examined whether clozapine induces more weight gain than haloperidol and whether weight gain is related to clinical improvement. METHOD: The weight and symptoms of 39 outpatients with schizophrenia who were randomly assigned to double-blind treatment with either clozapine or haloperidol were assessed. The weight and symptoms of 33 of the patients who chose to take clozapine during a 1-year follow-up after the study ended were also assessed. RESULTS: The patients treated with clozapine gained significantly more weight over baseline (7%) than the haloperidol-treated patients (1%). Weight gain was not significantly correlated with improvements in either positive or negative symptoms. Fifty-eight percent of the patients followed for 1 year gained at least 10% over their baseline weight. CONCLUSIONS: Weight gain is an important side effect of clozapine and is unrelated to the drug's differential antipsychotic efficacy.