What is the antibiotic of choice for treating Group A strep in patients allergic to penicillin?

Erythromycin is the antibiotic of choice for treating Group A streptococcal infections in patients who are allergic to penicillin. This choice is based on erythromycin's effectiveness against streptococcal bacteria, similar to penicillin but without the beta-lactam structure that can trigger allergic reactions in sensitive individuals.

Erythromycin belongs to the macrolide class of antibiotics, which work by inhibiting bacterial protein synthesis. This mechanism is particularly well-suited for treating infections caused by Group A strep (Streptococcus pyogenes), where effective alternatives to penicillin are necessary due to allergies.

While other antibiotics like ciprofloxacin or tetracycline may have spectrum activity against some strains, they are not typically first-line treatments for Group A strep and may have additional side effects or concerns, particularly in certain populations such as children. Amoxicillin, while a reasonable option for patients without penicillin allergy, is not suitable for those with such allergies and thus reaffirms the need for an alternative like erythromycin in these cases.