FCEM2-0800

A 65 year old patient arrives at the emergency department complaining of a productive cough and fever. The patient’s primary care physician had prescribed antibiotics a few days ago to treat a suspected respiratory infection. The patient’s INR is tested as they are on warfarin for atrial fibrillation. The INR comes back as 6.7.

Which of the following antibiotics is most likely to result in an extended INR?