(HealthDay News) – There is insufficient evidence to draw conclusions regarding the benefits of first-generation antipsychotics (FGAs) vs. second-generation antipsychotics (SGAs) for adults with schizophrenia, according to a study published online Aug 14 in the Annals of Internal Medicine.

Lisa Hartling, PhD, from University of Alberta in Edmonton, Canada, and colleagues compared the effects of FGAs with SGAs for the treatment of adult schizophrenia (aged 18–24 years) through a meta-analysis. Randomized trials and cohort studies lasting at least two years were included.

The researchers found few differences of clinical importance for core illness symptoms. For improving positive symptoms, there was moderate-strength evidence of a clinically important benefit of haloperidol over olanzapine, but the benefit was scale-dependent, with improvement seen in the Scale for the Assessment of Positive Symptoms but not in the Positive and Negative Syndrome Scale (PANSS). There was a clinically important benefit of olanzapine over haloperidol in improving negative symptoms, which was noted in both the PANSS and the Scale for the Assessment of Negative Symptoms, using moderate-strength evidence. There was no difference in mortality for chlorpromazine vs. clozapine or haloperidol vs. aripiprazole, based on low-strength evidence. Low-strength evidence also indicated an increased incidence of the metabolic syndrome for olanzapine vs. haloperidol and a higher incidence of tardive dyskinesia for chlorpromazine vs. clozapine. There was insufficient evidence to draw conclusions regarding diabetes mellitus.

“Existing studies on the comparative effectiveness of individual FGAs and SGAs preclude drawing firm conclusions because of sparse data and imprecise effect estimates,” the authors write. “The current evidence base is inadequate for clinicians and patients to make informed decisions about treatment.”

One author, in partnership with the University of Alberta, disclosed involvement with a patent regarding sodium nitroprusside for the treatment of schizophrenia.

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