Interaction of vitamin K antagonists and trimethoprim-sulfamethoxazole: ignore at your patient's risk.
The aim of the study was to summarize available literature regarding the interaction between vitamin K antagonists (VKAs) and trimethoprim-sulfamethoxazole (co-trimoxazole, TMP-SMX), and to provide recommendations for managing patient risk from this interaction. Data sources were English-language publications in the medical literature and Internet databases. Relevant publications that directly or indirectly addressed the VKA-TMP-SMX interaction were selected and reviewed. The mechanism of the VKA-TMP-SMX interaction, frequency of concurrent use, effect on international normalized ratio (INR), increased risk of bleeding, and strategies for risk reduction are summarized. The concurrent use of VKA and TMP/SMX rapidly and consistently raises INR and is associated with a two- to five-fold increase in bleeding. Concurrent use of VKA and TMP-SMX should be avoided when possible. When VKA and TMP-SMX are co-prescribed, VKA dose reduction is usually required. Patient education as well as early and frequent INR monitoring is recommended to reduce risk from this interaction.
Sarah Fetterman
SF
Hale
Timothy S
TS
Lesar
D000369:Aged, 80 and over; D000890:Anti-Infective Agents / Q000009:adverse effects*; D000925:Anticoagulants / Q000009:adverse effects*; D001778:Blood Coagulation Disorders / Q000139:chemically induced*; D004347:Drug Interactions; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000009:adverse effects*; D014812:Vitamin K / Q000037:antagonists & inhibitors*; D014859:Warfarin / Q000009:adverse effects*
D000890:Anti-Infective Agents; D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination