Even though penicillin was the first antibiotic, it is still the gold standard for the treatment of many susceptible infections, including pneumonia.

It is indicated for bacterial endocarditis, meningitis, lung abscess, community-acquired and aspiration pneumonias, syphilis, and septicaemia in children.

As a narrow-spectrum antibiotic, penicillin G targets non beta-lactamase Gram-positive organisms and limits the development of resistance better than broad-spectrum antibiotics. Its bactericidal effect is achieved through interfering with bacterial cell wall synthesis to cause cell lysis.

While some prescribers are concerned about the potential for diarrhoea from the opportunistic infection of Clostridium difficile, this is more commonly associated with broad-spectrum antibiotics such as cephalosporins, quinolones and lincosamides.

Penicillins are generally well tolerated, but the high sodium content should be considered in patients with heart failure, and the dose adjusted in patients with reduced creatinine clearance. Reported allergies should be investigated to eliminate simple adverse reactions, and cephalosporin cross-sensitivity considered.

Benzylpenicillin is administered intravenously, intramuscularly, or is released for up to four weeks from the intramuscular depot, benzathine penicillin.

During Antibiotic Awareness Week, start prescribing by the Antimicrobial Creed, using just enough of a targeted therapy with the narrowest spectrum, to get an effective outcome in the shortest time.


  1. Antibiotic Expert Group. eTG complete [Internet]. Melbourne: Therapeutic Guidelines Limited; 2013 July.
  2. Rossi S, ed. eAMH [online]. Adelaide: Australian Medicines Handbook, July 2013.

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