Amoxicillin / Clavulanate

(for veterinary information only)


62.5 mg, 125 mg, 250 mg,   
375 mg, 500 mg,        
625 mg, 1000 mg        
AS WELL AS           


Alexander Fleming wiki

Howard Walter Florey 1945 wiki

Ernst Boris Chain 1945 wiki

Alexander Fleming

 Howard Florey

Ernst Chain

(Photocredit all three images: Wikimedia Commons)

Thanks to work by Alexander Fleming (1881-1955), Howard Florey (1898-1968) and Ernst Chain (1906-1979), penicillin was first produced on a large scale for human use in 1943. At that time, the development of a pill that could reliably kill bacteria was remarkable and many lives were saved during World War II because this medication was available.

But quickly, it became obvious that this new "wonder drug" could bear improvement. For example:

  • Penicillin is not well absorbed from the intestinal tract meaning that at least 70% of an oral dose is wasted.
  • Penicillin is also a short-acting medication, with half of the amount circulating being removed from the body every half hour.
  • Not all bacteria have the type of cell wall which is susceptible to destruction by penicillin. (Bacteria are classified as Gram negative or Gram positive, depending on the cell wall characteristics. Penicillin is able to punch holes through the Gram positive cell wall but is not very effective against the Gram negative cell wall.)
  • Staphylococci (an important group of bacteria) quickly developed an enzyme to break the penicillin molecule apart and are thus rarely susceptible to penicillin. It is this phenomenon which is specifically targeted by the amoxicillin/clavulanic acid combination.

Amoxicillin represents a synthetic improvement upon the original penicillin molecule. Amoxicillin is better able to resist damage from stomach acid so less of an oral dose is wasted. While it is still susceptible to destruction by Staphylococcal enzymes, it does have a much broader spectrum against the Gram negative cell wall and is able to last a bit longer.

The combination of amoxicillin and clavulanic acid specifically addresses the problem with Staphylococci: the beta-lactamase enzyme and penicillinases that destroys penicillin antibiotics. Clavulanate protects the amoxicillin by binding to these bacterial enzymes so they cannot destroy the beta-lactam ring structure that makes the penicillin molecule so effective. In short, combining clavulanic acid and amoxicillin allows this medication to kill Staphylococci while ordinary amoxicillin would be ineffective.


Amoxicillin is regarded as having a fairly broad spectrum against many bacteria thus it is used both on organisms known to be sensitive to it plus it is a good selection when the sensitivity of bacteria is unknown. It is especially helpful in anaerobic infections (those which grow without the benefit of oxygen). Typical uses might include:

In short, anything amoxicillin can do, the combination drug will also do PLUS the combination can kill Staphylococci.


When the organism in a serious infection cannot be isolated, a common strategy is to attempt to "cover" for all possible bacteria. Amoxicillin is frequently used in combination with other antibiotics for this purpose.

This medication is believed to synergize with members of the fluorquinolone class of antibiotics (enrofloxacin, orbifloxacin, etc.)


Some individuals experience nausea with this medication. Giving the medication with food seems to reduce this effect.


The oral suspension should be refrigerated, though if it is mistakenly left out of the refrigerator for one day, this is not a problem. The oral suspension should be discarded after 10 days.

Amoxicillin-Clavulanic acid may be given with or without food.

Amoxicillin-Clavulanic acid will cross the placenta in a pregnant patient but is felt to be safe for use during pregnancy.

Page last updated: 3/11/2012