Final answer:
Of the drugs listed, Diltiazem Hydrochloride SR (diltiazem) and trimethoprim-sulfamethoxazole (Bactrim) interact with warfarin, potentially increasing the risk of bleeding.
Step-by-step explanation:
When considering which of the following drugs interact with warfarin/coumadin, it's important to note that warfarin (Coumadin) is a highly sensitive drug with a narrow therapeutic window and can interact with many substances. Of the options provided, b. Diltiazem Hydrochloride SR (diltiazem) and c. trimethoprimsulfamethoxazole (Bactrim) are known to interact with warfarin. Diltiazem is a calcium channel blocker which can enhance the effects of warfarin, potentially leading to an increased risk of bleeding. Trimethoprim-sulfamethoxazole, an antibiotic, can also potentiate warfarin's anticoagulant effect. On the other hand, a. Imodium (loperamide), an anti-diarrheal medication, and d. sumatriptan (Imitrex), a medication for migraines, are not commonly associated with significant interactions with warfarin.