Widely used in clinical settings, this antibiotic is effective against a range of Gram-positive bacteria, including streptococci, pneumococci, and meningococci. It is commonly administered intravenously or intramuscularly to treat serious infections such as bacterial endocarditis, meningitis, and septicemia. Due to its narrow spectrum and potency against susceptible organisms, it remains a first-line treatment for syphilis and tetanus. In research, it is used to select genetically modified cells in cell culture when paired with a resistance gene. Its use in veterinary medicine includes treatment of infections in livestock, although withdrawal periods are observed to prevent residues in food products.