Background: Speed of onset of therapeutic effect is an important dimension of drugs employed to treat psychosis and schizophrenia. Faster onset is desirable to reduce the anguish caused by delusions and hallucinations and to protect patients and others from the consequences of poor judgment associated with psychotic exacerbation. Although sufficient studies have demonstrated that novel antipsychotics have advantages over clinically employed doses of classic drugs in terms of tolerability and aspects of efficacy, less is known about differences in speed of onset of therapeutic effect. This report consists of a post hoc subanalysis of data from a large double-blind, randomized pivotal trial in which we compared onset of therapeutic effect between risperidone and haloperidol.

Method: During an 8-week period, 227 patients with DSM-III chronic schizophrenia received 4 mg/day of risperidone and 226 patients received 10 mg/day of haloperidol. Symptoms were assessed 6 times (days 0, 7, 14, 28, 42, and 56) using the Positive and Negative Syndrome Scale (PANSS) for schizophrenia and the Clinical Global Impressions-Severity of Illness scale (CGI-S). Data were analyzed using analysis of variance for multiple dependent variables and repeated-measures multivariate analysis of variance.

Results: The analyses revealed that patients receiving risperidone improved more rapidly than those receiving haloperidol as measured by PANSS total and CGI-S scores. Differences were most pronounced during the first week of treatment.

Conclusion: Results suggest that risperidone offers a more rapid response than haloperidol, particularly during the active phase of illness when time to response can be crucial.