Drug Interactions between caffeine and fluvoxamine

MONITOR: Coadministration with potent CYP450 1A2 inhibitors such as fluvoxamine may increase the plasma concentrations of caffeine in a dose-dependent manner. Caffeine is primarily metabolized by CYP450 1A2 and is considered a probe substrate for the isoenzyme. In 12 healthy volunteers, pretreatment with fluvoxamine for 7 days (10 mg once or twice a day) resulted in a 2-fold increase in the mean 24-hour area under the plasma concentration-time curve (AUC) of a single 100 mg oral dose of caffeine. When the dosage of fluvoxamine was increased (25 mg once or twice a day for 7 days), the mean 24-hour AUC of single-dose caffeine increased 5-fold. The peak plasma concentration (Cmax) of caffeine increased 40% and 141%, respectively, during these treatment phases. Another study found that fluvoxamine (50 mg daily for 4 days, then 100 mg daily for 8 days) decreased the median total clearance of a single 200 mg oral dose of caffeine by 80% and increased the half-life from 5 to 31 hours in eight healthy volunteers.

MANAGEMENT: Caution is advised if caffeine is administered concurrently with potent CYP450 1A2 inhibitors. Dosage adjustment should be considered in patients who experience excessive adverse effects of caffeine such as nausea, vomiting, headache, nervousness, irritability, agitation, restlessness, insomnia, tinnitus, tremors, and tachycardia.