Basics
Benzylpenicillin, also known as penicillin G, is an antibiotic used to treat a number of bacterial infections. These include pneumonia, streptococcal infections, syphilis, necrotizing enterocolitis, diphtheria, gas gangrene, leptospirosis, cellulitis, and tetanus. Benzylpenicillin is administered by injection into a vein or muscle.