Pfizerpen (generic: penicillin G potassium) is a prescription medication used to treat bacterial infections that affect the blood, heart, lungs, joints, and genital areas. Pfizerpen belongs to a group of drugs called penicillin antibiotics, which stop the growth of bacteria in the body.

This medication is available in an injectable form to be given directly into a vein (IV), the muscle (IM), the lining of the lungs, or the spine (IT) by a healthcare professional.

Common side effects of Pfizerpen include an allergic reaction, skin rash, and itching of the skin.