Clavulanic acid

Clavulanic acid (rINN) (IPA: ) is a beta-lactamase inhibitor (GlaxoSmithKline formerly Beecham) sometimes combined with penicillin group antibiotics to overcome certain types of antibiotic resistance. Specifically, it is used to overcome resistance in bacteria that secrete beta-lactamase enzymes, which otherwise inactivate most penicillins. Most commonly, the potassium salt potassium clavulanate is combined with amoxicillin (co-amoxiclav [brand name Augmentin] or the veterinary formulation Synulox from Pfizer) or ticarcillin.

The name is derived from the Streptomyces clavuligerus microorganisms from which clavulanic acid is derived. Clavulanic acid is biosynthetically generated from the amino acid arginine and the sugar glyceraldehyde 3-phosphate.

Mechanism of action
Clavulanic acid has negligible intrinsic antimicrobial activity, despite sharing the β-lactam ring that is characteristic of beta-lactam antibiotics. However, the similarity in chemical structure allows the molecule to act as a competitive inhibitor of beta-lactamases secreted by certain bacteria to confer resistance to beta-lactam antibiotics. This inhibition restores the antimicrobial activity of beta-lactam antibiotics against β-lactamase-secreting resistant bacteria. Despite this, some bacterial strains have emerged that are resistant to even such combinations.

Adverse effects
The use of clavulanic acid with penicillins has been associated with an increased incidence of cholestatic jaundice and acute hepatitis during therapy or shortly after, particularly in men and those aged over 65 years. The associated jaundice is usually self-limiting and very rarely fatal. (Joint Formulary Committee, 2004)

The UK Committee on Safety of Medicines (CSM) recommends that treatments such as amoxicillin/clavulanic acid preparations should be reserved for bacterial infections likely to be caused by amoxicillin-resistant β-lactamase-producing strains, and that treatment should not normally exceed 14 days.