A 75-year-old woman on Warfarin (INR 2.4) is started on Amoxicillin for LRTI. Five days later INR is 4.1. What is the MOST likely explanation?...

Question

A 75-year-old woman on Warfarin (INR 2.4) is started on Amoxicillin for LRTI. Five days later INR is 4.1. What is the MOST likely explanation?

Accepted Answer

Amoxicillin increases Warfarin effect by reducing vitamin K-producing gut flora and pharmacological interaction

Answer

Natural variability

Answer

Amoxicillin reduces absorption

Answer

Extra Warfarin doses

Answer

INR machine faulty

uk-dgm MCQ (SBA): Antibiotic-Warfarin INR Rise