Risperidone augmentation of clozapine: a critical review.

Objective: Atypical antipsychotics are frequently used as augmentation agents in clozapine-resistant schizophrenic patients. Risperidone (RIS) is the one most studied as a clozapine (CLZ) adjunct. The aim of this study is to critically review all published studies regarding the efficacy and safety of RIS as an adjunctive agent in CLZ-resistant schizophrenic or schizoaffective patients.

Methods: A MEDLINE search from January 1988 to June 2005 was conducted. Identified papers were examined against several clinical, pharmacological and methodological parameters.

Results: A total of 15 studies were found (2 randomized controlled trials, 3 open-label trials (OTs) and 8 case-studies (CSs)) comprising 86 schizophrenic or schizoaffective patients (mean age 38.4 years). Mean CLZ dosage during the combined treatment was 474.2 mg/day. Plasma CLZ levels were assessed in 62 patients (72.1%). RIS was added at a mean dosage of 4.6 mg/day for a mean of 7.9 weeks. Significant improvement in psychopathology was reported for 37 patients (43%). A lower RIS dosage and a longer duration of the trial seemed to be associated with a better outcome. Main side effects reported were: extrapyramidal symptoms or akathisia (9.3%), sedation (7%) and hypersalivation (5.8%).

Conclusions: Existing evidence encourages the use of RIS as an adjunctive agent in CLZ-resistant schizophrenic or schizoaffective patients.