Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 2D6 may increase the plasma concentrations of topical sofpironium, which has been shown to be partially metabolized by the isoenzyme. In a pharmacokinetic study in patients with primary axillary hyperhidrosis, sofpironium systemic exposure (AUC) and peak plasma concentration (Cmax) increased approximately 2-fold following concomitant use with the potent CYP450 2D6 inhibitor paroxetine at a 20 mg oral dose. Clinical data for sofpironium use in combination with other less potent CYP450 2D6 inhibitors are not available.

MANAGEMENT: Caution is advised when sofpironium topical is used concurrently with CYP450 2D6 inhibitors. Patients should be more closely monitored for adverse effects such as blurred vision, urinary retention, difficulty controlling body temperature in warm environments, and dry mouth.

ADJUST DOSING INTERVAL: Administration of atazanavir with food enhances oral bioavailability and reduces pharmacokinetic variability. According to the manufacturer, administration with a light meal increased the peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of a single 400 mg dose of atazanavir by 57% and 70%, respectively, relative to the fasting state. Administration with a high-fat meal resulted in a mean increase of 35% in atazanavir AUC and no change in Cmax compared to fasting. The coefficient of variation of AUC and Cmax decreased by approximately one-half when given with either a light or high-fat meal compared to the fasting state.

MANAGEMENT: To ensure maximal oral absorption, atazanavir should be administered with or immediately after a meal.