Active ingredient

Cephalexin for Animals: Mechanism, Doses by Species & Brands

Q: What is the cephalexin dose for dogs?

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

Q: What is the cephalexin dose for cats?

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

Reviewed by Dr. Ravi Baraiya, B.V.Sc.Updated 2 Nov 20262 sources

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].

Drug class: First-generation cephalosporin (beta-lactam) antibacterial
Sourced doses for: Dogs, Cats
Brands on this site: Lixen

Cephalexin dose calculator

Type the strength printed on your own product. Results are calculated in your browser from the cited doses on this page — always check the label of the product you use.

Cephalexin 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

What cephalexin is used for

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

How cephalexin works (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, contraindications and precautions

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].

Brands that contain cephalexin

Brand	Company	Contains	Market
Lixen	Virbac India	Cephalexin	India

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].

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Medically reviewed by

Dr. Ravi Baraiya, B.V.Sc.

Veterinarian · Reviewed 2 Nov 2026

References

Cephalosporins and Cephamycins Use in AnimalsMerck Veterinary Manual · 2025 · Veterinary reference
Passage read from this source
First-generation cephalosporins include cephaloridine, cephapirin, cefazolin, cephalexin, cephradine, and cefadroxil.
Only a few cephalosporins are acid stable and thus effective when administered PO.
Cephalexin should be anticipated to be ineffective against E coli.
15–45 mg/kg, PO, q 6–12 h
Beta-lactam Antimicrobial Use in AnimalsMerck Veterinary Manual · 2025 · Veterinary reference
Passage read from this source
Beta-lactam antimicrobials impair the development of bacterial cell walls by interfering with transpeptidase enzymes
The beta-lactam drug mimics the PBP substrate, thus inhibiting the PBP and subsequent cell wall synthesis.
Beta-lactam antimicrobials, when present in sufficient concentrations, are generally bactericidal toward most bacteria

For veterinary professionals. Information supports — never replaces — clinical judgement; always check the current product label and local regulations.