# Cephalexin for Animals: Mechanism, Doses by Species & Brands

> Cephalexin is a first-generation cephalosporin and one of the few cephalosporins that are acid stable and effective when given by mouth. Like other beta-lactams it inhibits bacterial cell wall synthesis.

- Source page: https://wevet.in/active-ingredients/cephalexin/
- Type: Active ingredient
- Publisher: WeVet
- Updated: 2026-11-02
- Medically reviewed by: Dr. Ravi Baraiya, B.V.Sc. (2026-11-02)
- Audience: veterinarians and veterinary students

Cephalexin is a first-generation cephalosporin [1] and one of the few cephalosporins that are acid stable and effective when given by mouth [1]. Like other beta-lactams it inhibits bacterial cell wall synthesis [2].

- Class: First-generation cephalosporin (beta-lactam) antibacterial
- Brands: Lixen

## Dose by species

| Species | Use | Dose | Route | How often | Basis |
|---|---|---|---|---|---|
| Dogs | Bacterial infections | 15–45 mg/kg [1] | PO | Every 6–12 hours | Reference |
| Cats | Bacterial infections | 15–35 mg/kg [1] | PO | Every 6–12 hours | Reference |

## Uses

- Oral cephalosporin for dogs and cats [1].
- Cephalexin should be anticipated to be ineffective against E. coli [1].

## Mechanism of action

Beta-lactam antimicrobials impair the development of bacterial cell walls by interfering with transpeptidase enzymes — the penicillin-binding proteins (PBPs) [2]. The drug mimics the PBP substrate and so inhibits cell wall synthesis; at sufficient concentrations beta-lactams are generally bactericidal [2].

## Safety

- Hypersensitivity reactions of several forms have occurred with cephalosporins, with cross-reactivity to penicillin allergies possible [1].
- Nausea, vomiting and diarrhoea may occasionally occur [1].


## Frequently asked questions

### What is the cephalexin dose for dogs?

15–45 mg/kg by mouth every 6–12 hours [1].

### What is the cephalexin dose for cats?

15–35 mg/kg by mouth every 6–12 hours [1].

### Does cephalexin work against E. coli?

Cephalexin should be anticipated to be ineffective against E. coli [1].

## References

[1] Cephalosporins and Cephamycins Use in Animals — Merck Veterinary Manual (2025). https://merckvetmanual.com/pharmacology/antibacterial-agents/cephalosporins-and-cephamycins-use-in-animals
[2] Beta-lactam Antimicrobial Use in Animals — Merck Veterinary Manual (2025). https://www.merckvetmanual.com/pharmacology/antibacterial-agents/beta-lactam-antimicrobial-use-in-animals

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Numbers in [brackets] cite the references above. For veterinary professionals. Information supports — never replaces — clinical judgement; always check the current product label and local regulations.
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