Drug Interaction Report

Consumer information for this interaction is not currently available.

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of mirtazapine, which is partially metabolized by the isoenzyme. In healthy study subjects, administration of mirtazapine (30 mg once daily) with the potent CYP450 3A4 inducer carbamazepine (400 mg twice daily) decreased mean steady-state mirtazapine peak plasma concentration (Cmax) and systemic exposure (AUC) by approximately 40% and 60%, respectively, compared to administration with placebo. In another study consisting of patients with unipolar depression receiving mirtazapine 45 mg daily, the addition of carbamazepine reportedly decreased mirtazapine plasma concentrations by approximately 47% after 3 weeks. Likewise, when mirtazapine 30 mg once daily was given with phenytoin 200 mg once daily in healthy, nonsmoking male volunteers, steady-state mirtazapine Cmax and AUC decreased by 33% and 47%, respectively, compared to mirtazapine given alone. Mirtazapine had no significant effect on the pharmacokinetics of either carbamazepine or phenytoin.

MANAGEMENT: The possibility of diminished therapeutic response to mirtazapine should be considered during coadministration with CYP450 3A4 inducers, particularly potent ones like carbamazepine, enzalutamide, lumacaftor, mitotane, phenobarbital, phenytoin, rifampin, and St. John's wort. Pharmacologic response to mirtazapine should be monitored more closely whenever a CYP450 3A4 inducer is added to or withdrawn from therapy, and the dosage adjusted as necessary.

Alcohol can increase the nervous system side effects of mirtazapine such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with mirtazapine. Do not use more than the recommended dose of mirtazapine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.