Drug Interaction Report

Consumer information for this interaction is not currently available.

MONITOR: Coadministration with inhibitors of CYP450 1A2 may substantially increase the plasma concentrations of melatonin. Data from available studies suggest that melatonin is primarily metabolized by CYP450 1A2, with possible contribution from CYP450 2C19 and 2C9. Coadministration of fluvoxamine, a potent CYP450 1A2 inhibitor that also inhibits CYP450 2C19 and 2C9, increased melatonin systemic exposure (AUC) by 17-fold and maximum plasma concentration (Cmax) by 12-fold. Contraceptives containing ethinyl estradiol, which can inhibit CYP450 1A2, may lead to a 4- to 5-fold increase in melatonin concentration. The risk of this interaction may be less likely to occur with estrogen products that have limited systemic absorption (e.g., vaginal, topical products).

MANAGEMENT: Caution is advised when melatonin is used concomitantly with CYP450 1A2 inhibitors. Patients should be monitored closely for adverse effects such as excessive drowsiness, headache, lethargy, dizziness, irritability, nervousness, restlessness, anxiety, abdominal pain, and dyspepsia.

Both smoking and excessive caffeine consumption can alter the blood levels of melatonin, which may affect the dosing. Tobacco smoking reduces, while caffeine increases melatonin blood levels. If you start smoking or undergo smoking cessation, your doctor may need to adjust the dose of melatonin. In addition, alcohol may reduce the effect of melatonin on sleep. It is best to avoid alcohol consumption during melatonin therapy. Talk to a healthcare professional if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.