title: Suspected trimethoprim/sulfamethoxazole-induced hypoprothrombinemia.
abstract: The following report illustrates a case of trimethoprim/sulfamethoxazole-induced hypoprothrombinemia in a patient receiving ongoing warfarin therapy for atrial fibrillation and aortic valve replacement. He was treated with trimethoprim/sulfamethoxazole (TMP/SMX) for sinusitis. During this time, the patient's prothrombin time international normalized ratio (INR) increased 3.5 times higher than the baseline value. The INR values decreased when the antibiotic was discontinued. If a patient is on warfarin and TMP/SMX is added, INR values should be monitored closely.
authors.affiliation: Pharmacy Practice Residency Program, West Virginia University Hospital, Morgantown 26506.
authors.forename: D E
authors.initials: DE
authors.lastname: Cook
authors.forename: C D
authors.initials: CD
authors.lastname: Ponte
mesh_terms: D000368:Aged; D001021:Aortic Valve; D001281:Atrial Fibrillation / Q000188:drug therapy; D004347:Drug Interactions; D006350:Heart Valve Prosthesis; D006801:Humans; D007020:Hypoprothrombinemias / Q000139:chemically induced*; D008297:Male; D011517:Prothrombin Time; D012852:Sinusitis / Q000188:drug therapy; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000009:adverse effects* / Q000494:pharmacology / Q000627:therapeutic use; D014859:Warfarin / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D014859:Warfarin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination