Question

A pharmacist calls the physician to report an increase in INR from 2.2 to 3.6 for a 65-year-old patient with atrial fibrillation who is being monitored on a warfarin protocol. What drug is MOST LIKELY to account for this observation?

1) Aspirin
2) Ibuprofen
3) Acetaminophen
4) Amoxicillin

Answer 1

The most likely drug to cause an increase in INR from 2.2 to 3.6 in a patient on warfarin is aspirin, which is a non-steroidal anti-inflammatory drug that can potentiate the effects of warfarin.

Step-by-step explanation:

The increase in INR from 2.2 to 3.6 in a 65-year-old patient with atrial fibrillation who is on a warfarin protocol could most likely be attributed to aspirin. Aspirin is a non-steroidal anti-inflammatory drug (NSAID) that inhibits platelet aggregation and is known to potentiate the effects of warfarin, thereby increasing the risk of bleeding and the INR level. The other drugs listed, such as ibuprofen and acetaminophen, may also affect the INR but are generally considered to have a less direct effect compared to aspirin, while amoxicillin is an antibiotic that isn't typically associated with significant changes in INR levels when used in the absence of other contributing factors.