benzylpenicillin

enUK

penicillin

[pen″ĭ-sil´in] any of a large group of natural or semisynthetic antibacterial antibiotics derived directly or indirectly from strains of fungi of the genus Penicillium and other soil-inhabiting fungi grown on special culture media. Penicillins exert a bacteriocidal as well as a bacteriostatic effect on susceptible bacteria by interfering with the final stages of the synthesis of peptidoglycan, a substance in the bacterial cell wall. Despite their relatively low toxicity for the host, they are active against many bacteria, especially gram-positive pathogens (streptococci, staphylococci, pneumococci); clostridia; certain gram-negative forms (gonococci and meningococci); certain spirochetes (Treponema pallidum and T. pertenue); and certain fungi. Certain strains of some target species, for example staphylococci, secrete the enzyme penicillinase, which inactivates penicillin and confers resistance to the antibiotic. Some of the newer penicillins, such as methicillin, are more effective against penicillinase-producing organisms. A class of extended-spectrum penicillins includes piperacillin and mezlocillin.
Penicillin is administered intramuscularly, orally, in liquid or tablet form, and topically in ointments. Oral administration requires larger doses of the drug because absorption is incomplete. Allergic reactions occur in some persons. The reaction may be slight—a stinging or burning sensation at the site of injection—or it can be more serious—severe dermatitis or even anaphylactic shock, which may be fatal.penicillin G the most widely used penicillin, used principally in the treatment of infections due to gram-positive organisms, gram-negative cocci, Treponema pallidum and Actinomyces israelii. The usual forms are salts such as penicillin benzathine, potassium, procaine, or sodium. Called also benzylpenicillin.penicillin V a biosynthetically or semisynthetically produced antibiotic similar to penicillin g, used orally in the form of the benzathine or potassium salt for mild to moderately severe infections due to susceptible gram-positive bacteria.

pen·i·cil·lin G

a commonly used penicillin compound; it comprises 85% of the penicillin salts: sodium, potassium, aluminum, and procaine, with the latter exerting prolonged action on intramuscular injection, because of limited solubility. An antibiotic obtained from the mold Penicillium chrysogenum used orally and parenterally; primarily active against gram-positive staphylococci and streptococci; destroyed by bacterial β-lactamase. Synonym(s): benzyl penicillin, benzylpenicillin