Penicillins: Uses & Side effects

Penicillins are a type of antibiotic derived from
Penicillium fungi. An antibiotic is a type of medicine that inhibits the growth
of, or kills, bacteria.

Penicillin G (also called benzylpenicillin) was
discovered by accident in 1928. Alexander Fleming, a Scottish
physician-scientist was growing a type of bacteria called Staphylococcus
on an uncovered petri dish when it became contaminated with mold
spores. He observed that the areas of bacteria near the mold were dying. He
isolated the substance from the mold that was killing the bacteria and called
it penicillin.

Another naturally occurring penicillin, penicillin V
was later isolated from the same mold. All other penicillins are semi-synthetic
(made by modifying the structure of the original naturally occurring
penicillins). Modification extends their spectrum of activity, allows them to
be taken orally, and increases their resistance against penicillinase, an
enzyme produced by some bacteria that inactivates penicillin.

Penicillins work by preventing the cross linking of amino acid chains in the bacterial cell wall. This does not affect pre-existing bacteria, but newly produced bacterial cells have weak cell walls that easily rupture.

are penicillins used for?

may be used to treat a wide range of infections caused by susceptible bacteria,
such as:

  • Dental abscess
  • Ear infections (eg, otitis media)
  • Gonorrhea
  • Pneumonia
  • Respiratory tract infections
  • Rheumatic fever
  • Scarlet fever
  • Skin infections
  • Urinary tract infections.


Penicillins generally cause few side effects. The most common side effects reported include abdominal pain, headache, rash, diarrhea, and taste perversion.

Penicillins may cause anaphylaxis in those allergic to penicillin, but the overall incidence of anaphylaxis is rare (0.01-0.05%).

some people may develop a super-infection due to overgrowth of a naturally
occurring bacterium called Clostridium difficile,
following use of any antibiotic, including penicillins. Symptoms may include
severe diarrhea.

Uncommonly, an overgrowth of the yeast, Candida albicans, may occur following penicillin use, resulting in the symptoms of thrush.

Keywords: Penicillins

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