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Schizophr Res. 2008 Feb;99(1-3):13-22. Epub 2007 Dec 3.

Weight gain induced by haloperidol, risperidone and olanzapine after 1 year: findings of a randomized clinical trial in a drug-naïve population.

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  • 1Department of Psychiatry, Marques de Valdecilla University Hospital, Avda. Valdecilla s/n, 39008, University of Cantabria, Spain.



There is little information about weight gain induced by antipsychotics at long-term.


To quantify the weight gain induced by first (haloperidol) and second generation antipsychotics (olanzapine and risperidone) in a cohort of drug-naïve subjects after 1 year of treatment.


This is a prospective, randomized clinical trial, including a representative sample of first episode psychotic incident cases from a population area of 555.000 people. The main outcome measures were changes in body weight and body mass index at 3 months and at 12 months. Both a per protocol analysis and an intention to treat analysis were conducted.


A total of 164 drug-naïve patients were included. At 12 months 144 patients were evaluated. Of them, 66% completed the protocol and 34% needed treatment switch. We found statistically significant differences in weight gain at 3 months: 3.8 kg (+/-4.1) for haloperidol, 5.9 kg (+/-5.1) for risperidone and 8.4 kg (+/-5.0) for olanzapine (F=7.045; p=0.002). After 1 year the difference in weight gain had disappeared: 9.7 kg (+/-5.7) for haloperidol, 8.9 kg (+/-8.8) for risperidone and 10.9 kg (+/-7.2) for olanzapine (F=0.817; p=0.445).


Drug-naïve patients experience an extraordinary weight gain after 1 year of treatment with haloperidol, olanzapine or risperidone. The main difference among these treatments is the pattern of weight gain but not the final amount of weight gain.

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