Pharmacotherapeutic group:

Antibacterials for systemic use, other beta-lactam antibacterials, first-generation cephalosporins.
ATCvet code: QJ01DB01.

Cefalexin is a semi-synthetic bactericidal antibiotic belonging to the cephalosporin group which acts by interference with bacterial cell wall formation.

Cefalexin is active against a wide range of Gram-positive and Gram-negative bacteria. The following micro-organisms have been shown to be sensitive to cefalexin in vitro: Staphylococcus spp (including penicillin-resistant strains), Streptococcus spp, Corynebacterium spp, Pasteurella multocida, Escherichia coli, Micrococcus spp, Moraxella spp.

Cefalexin is resistant to the action of staphylococcal penicillinase and is therefore active against the strains of Staphylococcus aureus that are insensitive to penicillin (or related antibiotics such as ampicillin or amoxycillin) because of production of penicillinase.

Cefalexin is also active against the majority of ampicillin-resistant E.coli.

Following oral administration, cefalexin is rapidly and almost completely absorbed. Peak plasma concentrations (Cmax= 14.38 μg/ml) are achieved within approximately 2 hours (Tmax= 2.1 hours) in the cat. Peak plasma concentrations in the dog (Cmax= 17.49 μg/ml) are achieved within approximately 1.5 hours (Tmax= 1.55). In both species, cefalexin is excreted in the urine in high concentrations and has an elimination half life (T1/2) of approximately 2.5–3 hours.