Abstract
Risperidone is extensively metabolized to an active metabolite, 9-hydroxyrisperidone (9-OH), which is dependent on renal clearance. Risperidone and 9-OH clearances are reduced in the elderly when compared to young subjects. The objective of this study was to determine whether among elderly subjects, risperidone and 9-OH clearance would further decline with increasing age and decreasing creatinine clearance (CrCl). Twenty geriatric inpatients were evaluated in a naturalistic setting with regard to total daily risperidone dose and dosing interval. Creatinine clear ance was determined using an 8-hour urine collection. Risperidone and 9-OH concentrations were determined by radioimmunoassay. Spearman's correlation coefficients were used to examine the impact of age and CrCl on con centrations of risperidone, 9-OH, their sum, and the quotient of 9-OH/risperidone. Mean age was 76.4 ± 9 years (range 56-91). Mean CrCl was 55.4 ± 32.8 mL/min/1.73 m2 (range 17-142 mL/min/1.73 m2). Mean risperidone daily dose was 1.3 ± 0.7 mg. Steady-state risperidone and 9-OH concentrations were 4.1 ± 5.3 ng/mL and 9.1 ± 6.2 ng/mL, respectively. Mean 9-OH/risperidone was 6.2 ± 6.1. Concentrations of risperidone, 9-OH, their sum, and 9-OH/risperi done were not significantly correlated with age or CrCl. These results were unchanged when concentrations were corrected for total daily risperidone dose. Among elderly subjects, risperidone and 9-OH clearance do not decline with increasing age or declining CrCl. (J Geriatr Psychiatry Neurol 2002; 15:77-81).
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