Risperidone (and 9-hydroxyrisperidone)

Risperidone (Risperidal®) is an atypical or ‘second generation’ antipsychotic. Side-effects of risperidone may include somnolence, nausea, dizziness, and anxiety. There is a risk of hypotension at higher doses. Risperidone can be administered either orally, or by intra-muscular injection. Oral dosage is normally 2-6 mg/d (BNF recommended limit). Patients receiving intra-muscular injection are normally given up to 50 mg every two weeks. Risperidone is metabolised by hydroxylation and N-demethylation. The 9-hydroxylated metabolite, 9-hydroxyrisperidone, is an active metabolite that also accumulates in plasma. Racemic 9-hydroxyrisperidone is itself licensed for the management of schizophrenia (Paliperidone®). Although a target range in therapy has not been established, a steady state reference range of 20-60 µg/L (risperidone + total 9-hydroxyrisperidone) has been suggested.