Family Nurse Practitioner Exam

Which medication is known to interact with warfarin and increase the risk of bleeding?

1. Trimethoprim/sulfamethoxazole (Bactrim DS)

2. Carafate (Sucralfate)

3. Losartan (Cozaar)

4. Furosemide (Lasix)

The correct answer is: Trimethoprim/sulfamethoxazole (Bactrim DS)

Trimethoprim/sulfamethoxazole, also known as Bactrim DS, is well-established to interact with warfarin, thereby increasing the risk of bleeding. This occurs because trimethoprim can inhibit the metabolism of warfarin and displace it from protein-binding sites, leading to higher levels of warfarin in the bloodstream. As a result, patients taking both medications may be at higher risk for increased International Normalized Ratio (INR) levels and, consequently, an elevated risk of hemorrhage. In contrast, the other medications listed do not share this significant interaction with warfarin. Sucralfate (Carafate) primarily acts locally in the gastrointestinal tract to protect against ulcers and does not significantly influence warfarin metabolism or its anticoagulant effects. Losartan (Cozaar), an angiotensin receptor blocker, does not substantially interact with warfarin, although monitoring is always advisable due to its impact on blood pressure and renal function. Furosemide (Lasix), a loop diuretic, may cause fluctuations in potassium and affect fluid status, but it does not have a notable effect on the anticoagulant properties of warfarin. Understanding these interactions is critical in