Benethamine Penicillin is an antibiotic that is effective against most gram-positive bacteria such as streptococci, staphylococci and pneumococci. Penicillin G derivatives are sometimes given orally to patients, but intramuscular injections are more often used because penicillin is released more slowly. In patients with hypersensitivity to penicillin, allergic reactions may occur when using it. Thus, benetamine penicillin is an effective broad-spectrum antibiotic that must be prescribed taking into account possible side effects.