Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 2C9 may increase the plasma concentrations of torsemide. The interaction has not been evaluated in pharmacokinetic studies; however, torsemide has been shown to undergo metabolism by CYP450 2C9.

MANAGEMENT: Caution is advised when torsemide is prescribed with CYP450 2C9 inhibitors. Patients should be monitored for potentially increased adverse effects such as dehydration, hypotension, electrolyte imbalances, hyperglycemia, tinnitus, and hearing loss.

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.