Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 3A4 and/or 2D6 may increase the plasma concentrations of aripiprazole, which is primarily metabolized by these isoenzymes. According to the product labeling, administration of a single 15 mg dose of aripiprazole during treatment with the potent CYP450 3A4 inhibitor ketoconazole (200 mg/day for 14 days) increased the systemic exposure (AUC) to aripiprazole and its active metabolite, dehydro-aripiprazole, by 63% and 77%, respectively, compared to administration of aripiprazole alone. Likewise, administration of a 10 mg dose of aripiprazole with the potent CYP450 2D6 inhibitor quinidine (166 mg/day for 13 days) increased aripiprazole AUC by 112%, although dehydro-aripiprazole AUC was reduced by 35%.

MANAGEMENT: Pharmacologic response to aripiprazole should be monitored more closely whenever a CYP450 3A4 and/or 2D6 inhibitor is added to or withdrawn from therapy, and the aripiprazole dosage adjusted as necessary. The manufacturer recommends that aripiprazole dosage be reduced to one-half the normal dosage during concomitant administration with ketoconazole or quinidine, and additional dosage adjustments be made based on clinical evaluation. No dosage recommendations are available for concomitant administration with less potent CYP450 2D6 or 3A4 inhibitors.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.