Following a myocardial infarct, a patient is stabilized on warfarin, with the dose adjusted to give a prothrombin time of 22 seconds. Which one of the following statements regarding potential drug interactions in this patient is accurate?
Warfarin binds extensively (98%) but weakly to plasma proteins and can be displaced by other drugs (e.g., ASA, chloral hydrate, phenytoin, sulfinpyrazone, and sulfonamides), resulting in an increase in its anticoagulant effects. Bile acid sequestrants bind acidic drugs like warfarin, preventing their GI absorption (| prothrombin time, PT), and cimetidine, which inhibits the metabolism of warfarin, causing an increase in PT. Vitamin K restores levels of prothrombin and several other coagulation factors, but the action is slow (24-48 h). Due to antiplatelet effects, even low doses of ASA may enhance bleeding in patients on warfarin.
Cholestyramine will increase prothrombin time.
Cimetidine is likely to decrease prothrombin time.
Antibacterial sulfonamides may enhance the effects of warfarin.
Vitamin K would restore prothrombin time to normal within 30 minutes.
Anti-Cancer