When taken in conjunction with warfarin, which drug can increase INR significantly?

Amiodarone is known to significantly increase the International Normalized Ratio (INR) when taken in conjunction with warfarin. This interaction occurs because amiodarone inhibits certain liver enzymes, specifically cytochrome P450 2C9, which is crucial for the metabolism of warfarin. As a result, the anticoagulant effects of warfarin are heightened, leading to an increased INR. An elevated INR indicates a higher risk of bleeding, which necessitates careful monitoring of patients who are prescribed both medications.

While other medications may also interact with warfarin, amiodarone's potent effect on warfarin metabolism makes it particularly significant when assessing the risk of increased INR. For example, aspirin, clopidogrel, and ibuprofen can have their own interactions with warfarin, but they do not typically produce the same degree of effect on INR as amiodarone does. Aspirin can increase bleeding risk but usually does not substantially elevate INR. Clopidogrel and ibuprofen may also impact bleeding risk, but they do not significantly alter warfarin's metabolic pathway in the same way amiodarone does.