A sinus infection in a patient recently treated with amoxicillin requires what next-step antibiotic?

• A. Prescribe amoxicillin again
• B. Do not prescribe an antibiotic; a decongestant is indicated only
• C. Prescribe a decongestant and antihistamine
• D. Prescribe amoxicillin-clavulanate today

Answer: (D)

When a sinus infection does not respond to initial amoxicillin, the next step is to broaden coverage to include bacteria that produce beta-lactamases. Amoxicillin-clavulanate does exactly that by adding clavulanate, which inhibits these enzymes and expands the spectrum to organisms commonly causing resistant sinusitis (such as Haemophilus influenzae and Moraxella catarrhalis, and penicillin-resistant strains of Streptococcus pneumoniae). This increases the chances of clearing the infection compared with continuing amoxicillin alone.

Decongestants or antihistamines don’t treat the bacterial infection itself, so they won’t reliably resolve symptoms. Repeating plain amoxicillin risks ongoing treatment failure due to beta-lactamase–producing organisms. Therefore, switching to amoxicillin-clavulanate is the most appropriate next step.