One of the MACROLIDES, it has an antibacterial spectrum similar, but not identical, to that of penicillin. The drug is a valuable alternative for patients who are allergic to penicillin. Erythromycin is used for respiratory infections, including spread within a family of WHOOPING-COUGH, and also CHLAMYDIA, LEGIONNAIRE'S DISEASE, SYPHILIS and enteritis caused by CAMPYLOBACTER. The drug may be given orally, intravenously or topically (for acne).