Select anti-infective agents such as co-trimoxazole, metronidazole, select quinolones, macrolides, azole antifungal agents, and isoniazid have been associated with prolonged international normalized ratio and/or bleeding.1 Few cases have been reported between doxycycline and warfarin.2,3 We report a case of possible retroperitoneal bleeding associated when these 2 drugs were administered concurrently.
Baciewicz AM, Bal BS. Bleeding Associated With Doxycycline and Warfarin Treatment. Arch Intern Med. 2001;161(9):1231. doi:10.1001/archinte.161.9.1231