This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.
Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
When these two medicines are taken together, your body may not process your blood-thinner properly.
What might happen:
You may experience an increased chance for bleeding including bleeding from your gums, nosebleeds, unusual bruising, or dark stools.
What you should do about this interaction:
Contact your healthcare professionals (e.g. doctor or pharmacist) about taking these two medicines together. They may already be aware of this interaction and may be monitoring you for it. If your doctor prescribes these medicines together, it may be necessary to check your bleeding times more often. The dose of your blood-thinner may need adjusting. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Barnett DB, Hancock BW. Anticoagulant resistance: an unusual case. Br Med J 1975 Mar 15;1(5958):608-9.
2.Hassall C, Feetam CL, Leach RH, Meynell MJ. Letter: Potentiation of warfarin by co-trimoxazole. Lancet 1975 Dec 6;2(7945):1155-6.
3.Lumholtz B, Siersbaek-Nielsen K, Skovsted L, Kampmann J, Hansen JM. Sulfamethizole-induced inhibition of diphenlhydantoin, tolbutamide, and warfarin metabolism. Clin Pharmacol Ther 1975 Jun;17(6):731-4.
4.Self TH, Evans W, Ferguson T. Letter: Interaction of sulfisoxazole and warfarin. Circulation 1975 Sep;52(3):528.
5.Tilstone WJ, Gray JM, Nimmo-Smith RH, Lawson DH. Interaction between warfarin and sulphamethoxazole. Postgrad Med J 1977 Jul;53(621):388-90.
6.Errick JK, Keys PW. Co-trimoxazole and warfarin: case report of an interaction. Am J Hosp Pharm 1978 Nov;35(11):1399-401.
7.O'Reilly RA, Motley CH. Racemic warfarin and trimethoprim-sulfamethoxazole interaction in humans. Ann Intern Med 1979 Jul;91(1):34-6.
8.O'Reilly RA. Stereoselective interaction of trimethoprim-sulfamethoxazole with the separated enantiomorphs of racemic warfarin in man. N Engl J Med 1980 Jan 3;302(1):33-5.
9.Kaufman JM, Fauver HE Jr. Potentiation of warfarin by trimethoprim-sulfamethoxazole. Urology 1980 Dec;16(6):601-3.
10.Sioris LJ, Weibert RT, Pentel PR. Potentiation of warfarin anticoagulation by sulfisoxazole. Arch Intern Med 1980 Apr;140(4):546-7.
11.Greenlaw CW. Drug interaction between co-trimoxazole and warfarin. Am J Hosp Pharm 1979 Sep;36(9):1155-6.
12.Perkash A. Experience with the management of deep vein thrombosis in patients with spinal cord injury. Part II: a critical evaluation of the anticoagulant therapy. Paraplegia 1980 Feb;18(1):2-14.
13.Brooks BJ Jr, Mocklin KE. Retropharyngeal hematoma as a complication of warfarin therapy. J La State Med Soc 1981 Oct;133(10):156-7.
14.Anonymous. Letter: Potentiations of warfarin by co-trimoxazole. Br Med J 1975 Jun 21;2(5972):684.
15.Serlin MJ. Antimicrobial drug interactions with oral anticoagulants. J Antimicrob Chemother 1979 Nov;5(6):628-30.
16.De Swiet J. Letter: Potentiation of warfarin by co-trimoxazole. Br Med J 1975 Aug 23;3(5981):491.
17.Anonymous. Warfarin potentiated by proguanil. BMJ 1991 Sep 28; 303(6805):789.
18.Koch-Weser J, Sellers EM. Drug interactions with coumarin anticoagulants (First of two parts). N Engl J Med 1971 Aug 26;285(9):487-98.
19.Weser JK, Sellers E. Drug interactions with coumarin anticoagulants. 2. N Engl J Med 1971 Sep 2;285(10):547-58.
20.Serlin MJ, Breckenridge AM. Drug interactions with warfarin. Drugs 1983 Jun;25(6):610-20.
21.Fischer HD, Juurlink DN, Mamdani MM, Kopp A, Laupacis A. Hemorrhage during warfarin therapy associated with cotrimoxazole and other urinary tract anti-infective agents: a population-based study. Arch Intern Med 2010 Apr 12;170(7):617-21.
22.Komatsu K, Ito K, Nakajima Y, Kanamitsu Si, Imaoka S, Funae Y, Green CE, Tyson CA, Shimada N, Sugiyama Y. Prediction of in vivo drug-drug interactions between tolbutamide and various sulfonamides in humans based on in vitro experiments. Drug Metab Dispos 2000 Apr;28(4):475-81.
23.This information is based on or an extract from the UW Metabolism and Transport Drug Interaction Database (DIDB) Platform, Copyright University of Washington 1999-2014..