Question 1
A 70-year-old with community-acquired pneumonia has a history of heart failure and an electrocardiogram showing a baseline QTc interval of 520 ms. Which antibiotic regimen is most appropriate?
▸ Why B is the answer
This patient requires broad coverage due to underlying comorbidities, but the prolonged QTc interval strictly contraindicates the use of macrolides (like azithromycin) and fluoroquinolones (like levofloxacin) due to the high risk of fatal arrhythmias such as torsades de pointes. A beta-lactam combined with doxycycline provides the necessary coverage for typical and atypical pathogens without affecting the cardiac conduction system. High-dose amoxicillin monotherapy lacks sufficient beta-lactamase stability for a patient with heart failure, and combining it with azithromycin introduces cardiac risk. Cefpodoxime with levofloxacin would dangerously exacerbate the existing electrical abnormality.
🔑 Key takeaway
Doxycycline should replace macrolides or fluoroquinolones in pneumonia combination therapy when patients have prolonged QTc intervals.

