Drug utilization review of risperidone for outpatients in a tertiary referral hospital in Singapore

Abstract

Background. Risperidone has been used in Singapore for schizophrenia since 1996. However, little information is available on its utilization pattern. Objective. To examine the risperidone utilization pattern in the Psychiatric Outpatient Clinic of the National University Hospital. Method. Medical records of all outpatients with schizophrenia prescribed with risperidone from 1 September1999 to 31 August 2000 were reviewed. Results. A total of 417 risperidone prescriptions were dispensed for 130 outpatients (50 male, 80 female) during the study period. The mean ± SD daily doses for prescriptions and for patients were 2.3 ± 1.3 mg and 2.1 ± 1.1 mg, respectively. Among these patients, 28 (21.5%) received at least one concomitant conventional antipsychotic and 71 (54.6%) received a concomitant anti-Parkinsonian agent. Logistic regression analysis suggested that a higher risperidone dose was associated with the greater probability of anti-Parkinsonian agent usage. Conclusions. The mean risperidone dose during the study period was towards the lower end of recommendation for schizophrenia. Further study is warranted to confirm and explain the pattern of low-dose risperidone, and the high use of concomitant conventional antipsychotics and anti-Parkinsonian agents in Singapore. Elucidation of these would provide a valuable insight for the management of Asian patients with schizophrenia using risperidone. However, the current data indicate that the practice of using a lower dose of risperidone could represent better affordability and an improved cost-effectiveness ratio of risperidone compared with conventional antipsychotics in Asian patients. Copyright © 2004 John Wiley & Sons, Ltd.