R_x: Finding Drug Information

Your favorite 65 year old patient is complaining of a 2 day history of fever, chest pain, and a productive cough with pinkish sputum. After a physical exam, you conclude that she has community-acquired pneumonia. You would like to treat her with antibiotics but note that she is currently on warfarin for her chronic atrial fibrillation and wonder if there is a drug interaction between warfarin and antibiotics. Should you use a penicillin (amoxicillin/clavulanic acid), a macrolide antibiotic (clarithroymycin or azithromycin), or a fluoroquinolone (levofloxacin)?