Add like
Add dislike
Add to saved papers

Serious bleeding events due to warfarin and antibiotic co-prescription in a cohort of veterans.

BACKGROUND: Antibiotics may interact with warfarin, increasing the risk for significant bleeding events.

METHODS: This is a retrospective cohort study of veterans who were prescribed warfarin for 30 days without interruption through the US Department of Veterans Affairs between October 1, 2002 and September 1, 2008. Antibiotics considered to be high risk for interaction with warfarin include: trimethoprim/sulfamethoxazole (TMP/SMX), ciprofloxacin, levofloxacin, metronidazole, fluconazole, azithromycin, and clarithromycin. Low-risk antibiotics include clindamycin and cephalexin. Risk of bleeding event within 30 days of antibiotic exposure was measured using Cox proportional hazards regression, adjusted for demographic characteristics, comorbid conditions, and receipt of other medications interacting with warfarin.

RESULTS: A total of 22,272 patients met inclusion criteria, with 14,078 and 8194 receiving high- and low-risk antibiotics, respectively. There were 93 and 36 bleeding events in the high- and low-risk groups, respectively. Receipt of a high-risk antibiotic (hazard ratio [HR] 1.48; 95% confidence interval [CI], 1.00-2.19) and azithromycin (HR 1.93; 95% CI, 1.13-3.30) were associated with increased risk of bleeding as a primary diagnosis. TMP/SMX (HR 2.09; 95% CI, 1.45-3.02), ciprofloxacin (HR 1.87; 95% CI, 1.42-2.50), levofloxacin (HR 1.77; 95% CI, 1.22-2.50), azithromycin (HR 1.64; 95% CI, 1.16-2.33), and clarithromycin (HR 2.40; 95% CI, 1.16-4.94) were associated with serious bleeding as a primary or secondary diagnosis. International normalized ratio (INR) alterations were common; 9.7% of patients prescribed fluconazole had INR value >6. Patients who had INR performed within 3-14 days of co-prescription were at a decreased risk of serious bleeding (HR 0.61; 95% CI, 0.42-0.88).

CONCLUSIONS: Warfarin users who are prescribed high-risk antibiotics are at higher risk for serious bleeding events. Early INR evaluation may mitigate this risk.

Full text links

We have located links that may give you full text access.
Can't access the paper?
Try logging in through your university/institutional subscription. For a smoother one-click institutional access experience, please use our mobile app.

For the best experience, use the Read mobile app

Mobile app image

Get seemless 1-tap access through your institution/university

For the best experience, use the Read mobile app

All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.

By using this service, you agree to our terms of use and privacy policy.

Your Privacy Choices Toggle icon

You can now claim free CME credits for this literature searchClaim now

Get seemless 1-tap access through your institution/university

For the best experience, use the Read mobile app