Risperidone (Risperdal): clinical experience with a new antipsychosis drug.

Risperidone (Risperdal) is a benzisoxazole derivative with a high affinity for serotonin 5-HT2 and dopamine D2 receptors, and some affinity for alpha- adrenergic, histamine H1 and dopamine D1 receptors. It has no anticholinergic effects. Early studies demonstrated risperidone to be an effective medication for psychotic symptoms, probably more so than the older neuroleptics for both positive and negative symptoms. At clinically effective doses, risperidone causes no more extrapyramidal side-effects (EPS) than placebo; at higher doses EPS frequency increases in a dose-dependent manner. Since it became available in 1994, extensive experience with the drug supports favourable early impressions of efficacy and tolerability. Minimal sedation, relatively little weight gain and absence of anticholinergic manifestations contribute to the relative tolerability of risperidone as compared to older neuroleptics. However, risperidone is associated with hyperprolactinaemia which can result in amenorrhoea and sexual dysfunction. Compared to older neuroleptics, pharmacoeconomic studies have shown that use of risperidone is associated with reduced hospitalisation and direct cost savings. A recent study found equivalent efficacy between risperidone and clozapine for treatment-resistant patients. Two studies comparing risperidone and olanzapine have yielded positive but conflicting findings. The overall positive experience with risperidone has resulted in the drug being widely recommended as a first line treatment option for psychoses.