Risperidone Drug Monitoring: A Useful Clinical Tool?

ISSN： 1173-2563

Source： Clinical Drug Investigation, Vol.19, Iss.4, 2000-04, pp. : 283-292

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Abstract

Background: Risperidone is an atypical antipsychotic drug that has been marketed in France since 1996. Therapeutic failures have been observed with risperidone.Objective: To investigate whether interactions with the cytochrome P450 (CYP) isoenzymes implicated in risperidone metabolism could explain these treatment failures.Design and Setting: This was a retrospective study of clinical and drug monitoring data from 50 patients treated by five psychiatrists in northern France.Methods: The concentration of active drug (risperidone + 9-hydroxy-risperidone) in serum was evaluated by high performance liquid chromatography and radio receptor assay. Clinical efficacy was assessed by the global improvement (CGI) item of the Clinical Global Impression rating scale.Results: Statistical analysis revealed a significant increase in efficacy when the serum concentration of active drug was between 25 and 150 µg/L compared with when it was out of this range. Carbamazepine, a CYP3A4 inducer, dramatically decreased the concentration of the active moiety of risperidone; on the contrary, CYP3A4 inhibitors (alprazolam and valproic acid) increased the concentration of active drug. The metabolism of risperidone by CYP3A4 did not lead to the formation of metabolite(s) with anti-D dopaminergic activity. Drugs interacting with CYP2D6 altered the risperidone/9-hydroxy-risperidone ratio but did not change the total amount of active drug.Conclusions: We have established a therapeutic range for risperidone. CYP3A4 is a major pathway for risperidone metabolism. Consideration of these factors in clinical practice should lead to improved outcomes for patients treated with risperidone.