WARFARIN RESISTANCE IN A PATIENT WITH SHORT-BOWEL SYNDROME

Drug therapy in short bowel syndrome can be complicated by inadequate or incomplete absorption of drugs in the small intestine. Many case re ports claim that warfarin absorption is not affected by the syndrome. We treated a patient with oral warfarin for recurring deep vein thromb osis; up to 20 mg/day was administered with no increase in the interna tional normalized ratio. Drug-drug interactions that may prevent absor ption, increase metabolism, or antagonize the effects of warfarin were ruled out. Intravenous lipid administration, which is anecdotally rep orted to precipitate warfarin resistance, may have contributed to the condition, but dosing was less frequent than in published reports. The most probable explanation of warfarin resistance is the reduced surfa ce area for drug absorption secondary to surgical removal of the patie nt's duodenum and gastrojejunostomy.