This case report further establishes the inhibitory effects of paroxetine on risperidone (R) metabolism in a patient whose R was discontinued due to side effects. Baseline through levels in ng/ml were 33 for R, 9 for 9-hydroxyrisperidone (9-OHR) and 42 for the total moiety. The fourth morning after R discontinuation, levels were 4 for R, 1 for 9-OHR and 5 for the total moiety. The estimated half-lives were 23.8 hours for R, 22.8 hours for 9-OHR and 23.5 hours for the total moiety.
