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. 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, for example, methicillin, are more effective against penicillinase-producing organisms. 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 reaction to penicillin occurs in some persons. All rights reserved.