Drug Interaction Report

MONITOR CLOSELY: Coadministration of foscarnet and parenteral pentamidine may cause severe hypocalcemia. Renal impairment and symptomatic hypocalcemia (Trousseau's and Chvostek's signs) have been observed during concomitant therapy, and fatalities have been reported rarely in postmarketing surveillance. An interaction is suspected based on presumed additive effects on serum calcium. In addition, both drugs may have additive nephrotoxic effects.

MANAGEMENT: Close monitoring is recommended during concomitant use of foscarnet and parenteral pentamidine. Serum creatinine and electrolyte levels should be assessed prior to initiating therapy and frequently during therapy. Patients should be advised to promptly notify their physician if they experience potential symptoms of hypocalcemia such as perioral tingling, numbness in extremities, and paresthesias.