Zithromax Zithromax. Drug and Patient Information. Dosage. Overdose. Generic or Brand Zithromax. For Professionals and Consumers. Zithromax is an antibiotic related to erythromycin. It is prescribed for adults to treat certain mild to moderate skin infections; upper and lower respiratory tract infections, including pharyngitis (strep throat), tonsillitis, worsening of chronic obstructive pulmonary disease, and pneumonia; [...]