Hypercoagulation from Concomitant Administration of Tamoxifen and Warfarin

Tamoxifen causing an increase in the anticoagulation effect of warfarin is suggested to be clinically significant, but cases so far have been largely undocumented. Current recommendations advise clinicians to proceed with caution during concomitant therapy. In the presence of other medications known to interact with warfarin, such as antibiotics, proton pump inhibitors, amiodarone, and azole antifungals, international normalized ratio (INR) elevations can possibly be exacerbated even further. We hereby present a case report and a review of significant literature on the use of tamoxifen and warfarin concurrently.