Drug Interactions between alvimopan and Bactrim

MONITOR: Two cases have been reported in which patients on sulfamethoxazole-trimethoprim therapy, after consuming beer, reported flushing, heart palpitations, dyspnea, headache, and nausea (disulfiram - alcohol type reactions). First-generation sulfonylureas have been reported to cause facial flushing when administered with alcohol by inhibiting acetaldehyde dehydrogenase and subsequently causing acetaldehyde accumulation. Since sulfamethoxazole is chemically related to first-generation sulfonylureas, a disulfiram-like reaction with products containing sulfamethoxazole is theoretically possible. However, pharmacokinetic/pharmacodynamic data are lacking and in addition, the two reported cases cannot be clearly attributed to the concomitant use of sulfamethoxazole-trimethoprim and alcohol.

MANAGEMENT: Patients should be alerted to the potential for this interaction and although the risk for this interaction is minimal, caution is recommended while taking sulfamethoxazole-trimethoprim concomitantly with alcohol.

Coadministration with a high-fat meal may decrease the rate and extent of alvimopan absorption. According to the product labeling, alvimopan peak plasma concentration (Cmax) and systemic exposure (AUC) were decreased by approximately 38% and 21%, respectively, and the time to reach peak plasma concentration (Tmax) was prolonged by approximately 1 hour when taken with a high-fat meal. The clinical significance is unknown. In postoperative ileus clinical trials, the preoperative dose of alvimopan was administered in a fasting state, and subsequent doses were given without regard to meals.