Penicillin Mechanism of Action

Penicillin (sometimes abbreviated PCN or pen) is a group of Beta-lactam antibiotics used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms.

Developments from penicillin

The first major development was ampicillin, which offered a broader spectrum of activity than either of the original penicillins. Further development yielded beta-lactamase-resistant penicillins including flucloxacillin, dicloxacillin and methicillin. These were significant for their activity against beta-lactamase-producing bacteria species, but are ineffective against the methicillin-resistant Staphylococcus aureus strains that subsequently emerged.

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The line of true penicillin was the antipseudomonal penicillins, such as ticarcillin and piperacillin, useful for their activity against Gram-negative bacteria. However, the usefulness of the beta-lactam ring was such that related antibiotics, including the mecillinams, the carbapenems and, most important, the cephalosporins, have this at the center of their structures.

Penicillin bind to protein called penicillin binding protein or PBP which are bacterial enzymes that catalyze cell wall peptidoglycon synthesis, this binding interferes with cell wall synthesis and leads to cell lysis and destruction of bacterium, Natural penicillin is effective against Gram-positive cocci and anaerobic pathogen and Spirochete.Penicillin G is also effective against Gram-Negative coccus. Semi synthetic penicillin which are chemically synthesized analogs are effective against gram-negative bacilli, Penicillin G is first commercially available penicillin .it is fully absorbed when administered orally. Due to acid inactivation in the stomach. But well absorbed if administered intra-muscularly. The drug is also excreted rapidly in the urine Penicillin V and some semi-synthetic such as ampicillin, which are resistant to acid and so administered orally, subsequently better absorbed have greater bio availability and extended duration of action.