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.