A patient with seasonal allergic rhinitis is being treated with terfenadine and subsequently develops cardiac arrhythmias after receiving a course of antibiotics. Which antibiotic is most likely responsible for this adverse effect?

Explanation

Erythromycin is known to inhibit the metabolism of terfenadine, leading to increased plasma levels of terfenadine and a risk of cardiac arrhythmias such as QT prolongation and torsades de pointes. Other antibiotics like ampicillin, tetracycline, and co-trimoxazole do not typically cause this interaction.