The full content of Annals is available to subscribers

Subscribe/Learn More  >
Original Research |

Racemic Warfarin and Trimethoprim-Sulfamethoxazole Interaction in Humans

[+] Article, Author, and Disclosure Information

▸Requests for reprints should be addressed to Robert A. O'Reilly, M.D.; Department of Medicine, Santa Clara Valley Medical Center; 751 South Bascom Avenue; San Jose, CA 95128.

San Jose and San Francisco, California

Ann Intern Med. 1979;91(1):34-36. doi:10.7326/0003-4819-91-1-34
Text Size: A A A

Eleven normal humans were studied to evaluate the reported interaction of racemic sodium warfarin and trimethoprim-sulfamethoxazole prospectively. Single oral doses of racemic warfarin, 1.5 mg/kg of body weight, were administered with and without 320 mg of trimethoprim and 1600 mg of sulfamethoxazole orally, beginning 7 d before the warfarin and continuing daily throughout the hypoprothrombinemia. Daily plasma samples were analyzed for one-stage prothrombin activity (Quick) and for warfarin content by high-pressure liquid chromatography. Transient cutaneous reactions developed in four of 11 subjects: a morbilliform rash in three (studies discontinued) and generalized pruritus in one. A highly significant augmentation of the warfarin effect on the mean one-stage prothrombin activity (P < 0.003) occurred with trimethoprim-sulfamethoxazole, but no significant effect was found on the warfarin half-life (P > 0.5). It is concluded that trimethoprim-sulfamethoxazole interacts with racemic warfarin, possibly at a receptor-site locus.





Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).


Submit a Comment/Letter
Submit a Comment/Letter

Summary for Patients

Clinical Slide Sets

Terms of Use

The In the Clinic® slide sets are owned and copyrighted by the American College of Physicians (ACP). All text, graphics, trademarks, and other intellectual property incorporated into the slide sets remain the sole and exclusive property of the ACP. The slide sets may be used only by the person who downloads or purchases them and only for the purpose of presenting them during not-for-profit educational activities. Users may incorporate the entire slide set or selected individual slides into their own teaching presentations but may not alter the content of the slides in any way or remove the ACP copyright notice. Users may make print copies for use as hand-outs for the audience the user is personally addressing but may not otherwise reproduce or distribute the slides by any means or media, including but not limited to sending them as e-mail attachments, posting them on Internet or Intranet sites, publishing them in meeting proceedings, or making them available for sale or distribution in any unauthorized form, without the express written permission of the ACP. Unauthorized use of the In the Clinic slide sets will constitute copyright infringement.


Buy Now for $42.00

to gain full access to the content and tools.

Want to Subscribe?

Learn more about subscription options

Topic Collections
PubMed Articles
Forgot your password?
Enter your username and email address. We'll send you a reminder to the email address on record.