Which species have cited Cephalexin dosing data?

Cephalexin dosing in the ExoticRx formulary covers 3 species: Cat (Domestic), Dog (Domestic), Guinea Pig.

Is Cephalexin a controlled substance?

Cephalexin is not federally scheduled in the US. Controlled-drug status differs by country — verify your local rules.

What are the side effects of Cephalexin?

Reported side effects, adverse reactions, and contraindications for Cephalexin: May cause GI upset. Use with caution in penicillin-allergic animals (cross-reactivity). Not effective against Pseudomonas.

Cephalexin

US brand names:Keflex

Also known as: Cefalexin

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Contraindicated in Rabbit, Guinea Pig, Chinchilla, Hamster, Degu

Rabbit: Oral beta-lactams cause fatal dysbiosis in rabbitsOral amoxicillin (and other oral beta-lactams) selectively destroy gram-positive hindgut flora in rabbits, allowing Clostridium spiroforme overgrowth and fatal enterotoxemia. Never administer oral beta-lactams to rabbits. Parenteral administration carries a lower risk than the oral route, but is not established as safe in rabbits.
Guinea Pig: Oral beta-lactams cause fatal dysbiosis in guinea pigsOral amoxicillin reliably causes Clostridium difficile-mediated fatal enterotoxemia in guinea pigs. Same mechanism as in rabbits. Parenteral administration carries a lower risk than the oral route; parenteral ceftiofur specifically has been given to guinea pigs and chinchillas without adverse effect.
Chinchilla: Oral beta-lactams cause fatal dysbiosis in chinchillasChinchillas are hindgut fermenters with the same flora dependence as rabbits and guinea pigs. Oral penicillins and oral cephalosporins trigger Clostridium overgrowth and fatal enterotoxemia. Never give oral beta-lactams; parenteral routes and trimethoprim-sulfa, fluoroquinolones, or chloramphenicol are the safer choices.

Hamster: Oral beta-lactams cause fatal enterocolitis in hamstersHamsters are exquisitely susceptible to antibiotic-associated Clostridium difficile enterocolitis — the hamster is the classic laboratory model for it. Oral penicillins and cephalosporins are reliably fatal. Never administer oral beta-lactams.

Degu: Oral beta-lactams risk fatal dysbiosis in degusDegus are caviomorph hindgut fermenters closely related to chinchillas and guinea pigs. Degu-specific data is limited, so this warning is extrapolated from those related hystricomorphs — but the shared physiology makes oral beta-lactam enterotoxemia the expected outcome. Treat as contraindicated; use the safer alternatives.

Sourced from published veterinary references. Awaiting credentialed clinical reviewer — our editorial process.

Cephalexin is dosed at 15–25 mg/kg PO q8-12h in guinea pigs, per Carpenter's Exotic Animal Formulary, 6th Ed. Verify against current literature before clinical use.

Drug Class

Antibiotic

Routes

Indications

Bite wound infectionsBone/joint infections (sensitive organisms)Deep pyodermaDental abscessFeline acnePost-surgical wound infection prophylaxispyodermaSkin infectionsSuperficial pyodermaUncomplicated UTIUTIWound infections

Mechanism of Action

Inhibits bacterial cell wall synthesis by binding to PBPs. First-generation cephalosporin with good gram-positive coverage.

Side effects & warnings

May cause GI upset. Use with caution in penicillin-allergic animals (cross-reactivity). Not effective against Pseudomonas.

Species with Cephalexin dosing data (12 dose rules)

Cat (Domestic)Dog (Domestic)Guinea Pig

Species references:All Cat (Domestic) drugs All Dog (Domestic) drugs All Guinea Pig drugs

Evidence levels across 12 dose rules

Strong×8Moderate×3Extrapolated×1

Each ExoticRx dose rule is graded by the strength of its primary evidence — see the editorial process.

Backed by 6 published sources

· Carpenter's Exotic Animal Formulary, 6th Ed
· Hillier A, Lloyd DH, Weese JS, et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (antimicrobial guidelines working group of the international society for companion animal infectious diseases). Vet Dermatol. 2014;25:163-e43. — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.263 (2026-08-01).
· Plumb's Veterinary Drug Handbook, 9th Ed
· Plumb's Veterinary Drug Handbook, 9th Ed, p.263, DOGS — susceptible skin infections (extra-label) a); superscript 1 resolves to Hillier A, Lloyd DH, Weese JS, et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the ISCAID). Vet Dermatol. 2014;25:163-e43
· Therios Chewable Tablets for Cats [Product Label; UK). Ceva Animal Health; 2018. — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.263 (2026-08-01).
· Weese JS, Blondeau J, Boothe D, et al. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. Vet J. 2019;247:8-25. — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.263 (2026-08-01).

Sample dosing (2 of 12 cited rules)

A dog/cat sample is shown here. Cited dosing for all 3 species — reptiles, birds, pocket pets, livestock, and equine — is free on the per-species pages above. Pro adds the weight-based calculator for every species.

Species	Route	Dose	Frequency	Evidence	Source
Dog (Domestic)	PO	22–30 mg/kg	q8h	Strong	Plumb's Veterinary Drug Handbook, 9th Ed
Dog (Domestic)	PO	22–30 mg/kg	q12h	Strong	Hillier A, Lloyd DH, Weese JS, et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (antimicrobial guidelines working group of the international society for companion animal infectious diseases). Vet Dermatol. 2014;25:163-e43. — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.263 (2026-08-01).

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