Drug Interaction Report

MONITOR: Theoretically, topical administration of minoxidil may potentiate the hypotensive effects of systemic minoxidil and other vasodilators. Although systemic absorption of topical minoxidil is generally minimal (approximately 1.6% to 3.9% of an applied dose), adverse cardiovascular effects such as edema, palpitations, blood pressure decreases, and increased pulse rate have been reported in a few patients. Increased systemic absorption may occur when topical minoxidil is used in excess of normally recommended dosages or applied to compromised skin.

MANAGEMENT: Patients prescribed topical minoxidil in combination with systemic vasodilators or peripherally-acting antiadrenergic agents should be monitored for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache.

ADJUST DOSING INTERVAL: Food may reduce the oral bioavailability of silodosin. The effect of a moderate-fat, moderate-calorie meal on silodosin pharmacokinetics was variable and decreased silodosin maximum plasma concentration (Cmax) by approximately 18% to 43% and systemic exposure (AUC) by 4% to 49% across three different studies. The maximum effect of food (i.e., coadministration with a high-fat, high-calorie meal) on the pharmacokinetics of silodosin was not evaluated. Safety and efficacy clinical trials for silodosin were always conducted in the presence of food intake.

MANAGEMENT: Patients should be instructed to take silodosin with a meal to reduce the risk of adverse events.