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 mg/kg SC q12h in rabbits, per Carpenter's Exotic Animal Formulary, 6th Ed — Carpenter's Exotic Animal Formulary 6th ed, Table 10.1 (Antimicrobial Agents Used in Rabbits.a). — Carpenter's Exotic Animal Formulary 6th ed, Table 10.1 (Antimicrobial Agents Used in Rabbits.a). Verify against current literature before clinical use.
Each ExoticRx dose rule is graded by the strength of its primary evidence — see the editorial process.
Sample dosing (2 of 25 cited rules)
A dog/cat sample is shown here. Cited dosing for all 15 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.
Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.234, Cephalexin monograph spanning p.234-236.Compilation only — we have not located an independent source that prints this figure.
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. — Plumb's 10th ed printed p.234, Cephalexin monograph spanning p.234-236.Compilation only — we have not located an independent source that prints this figure.
· 133. Bush M, Locke D, Neal LA, et al. Pharmacokinetics of cephalothin and cephalexin in selected avian species. Am J Vet Res. 1981;42:1014-1017. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.408 doi:10.2460/ajvr.1981.42.06.1014 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· 133. Bush M, Locke D, Neal LA, et al. Pharmacokinetics of cephalothin and cephalexin in selected avian species. Am J Vet Res. 1981;42:1014-1017. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.408 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· 376. Harlin RW. Pigeons. Vet Clin North Am Small Anim Pract. 1994;24:157-173. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.408 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
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· 391. Hawkins MG, Barron H, Speer BL, et al. Birds. In: Carpenter JW, eds. Exotic Animal Formulary, 4th ed., Elsevier Saunders, St. Louis, MO; 2013:183-437. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.408 — Carpenter 6th ed, Table 5.6 is not involved - the row is in Table 5.1 (Antimicrobial Agents Used in Birds), Cephalexin block. NOTE the served reference is Carpenter citing its OWN 4th edition (ref 391), so the ultimate provenance of 40-100 mg/kg remains unestablished.
· 51. Flecknell PA. Analgesia and post-operative care. Laboratory Animal Anaesthesia; 2016:141-192. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.771 doi:10.1016/b978-0-12-800036-6.00004-1 — Carpenter's Exotic Animal Formulary 6th ed, Table 9.1 (Antimicrobial and Antifungal Agents Used in Rodents.a).
· BSAVA Small Animal Formulary, 10th ed, Part A (Canine and Feline) — Cefalexin (Cephalexin), DOSES, printed p.68: "Cats: 15 mg/kg p.o. q8-12h. Increased doses (20-30mg/kg p.o. q8-12h) should be used for […]"
· BSAVA Small Animal Formulary, 10th ed, Part A (Canine and Feline) — Cefalexin (Cephalexin), DOSES, printed p.68: "Cats: 15 mg/kg p.o. q8-12h; 10 mg/kg i.m., s.c. q24h. Increased doses (20-30mg/kg p.o. q8-12h) […]"
· BSAVA Small Animal Formulary, 10th ed, Part A (Canine and Feline) — Cefalexin (Cephalexin), DOSES, printed p.68: "Increased doses (20-30mg/kg p.o. q8-12h) should be used for superficial pyoderma and to treat […]" Corroborating: Papich MG. Saunders Handbook of Veterinary Drugs, 5th ed, printed p.144: "Dogs •. For other infections: 10-30 mg/kg q6-12h PO." — EDITION UNVERIFIABLE 2026-08-07: this citation names Papich 5th ed, which is NOT held. Its page locator does not resolve to a page naming this drug in the 4th ed (2016), so the reference cannot be confirmed against any copy available here. Treat the page number as unchecked and consult the 5th edition directly.
· Carpenter Exotic Animal Formulary 6th ed, Table 9.1 (Antimicrobial and Antifungal Agents Used in Rodents), Cephalexin, row Hamsters, gerbils. SOURCE CONFLICT DISCLOSED: Carpenter attributes this row to ref 130 = Morrisey JK, Carpenter JW. Formulary. In: Quesenberry KE, Carpenter JW, eds. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, 4th ed. Elsevier, St. Louis, MO -- 2021:620-630 -- but that source, Appendix Table A.1, Gerbils/Hamsters column, prints 25 mg/kg SC q12h, not q24h. The served q24h is Carpenter own printed interval and the lower daily exposure of the two. — SOURCE ROW: Carpenter's Exotic Animal Formulary 6th ed, Table 9.1 — "Cephalexin. 25 mg/kg SC q24h(130). Hamsters, gerbils". Superscript 130 resolves to Morrisey & Carpenter, Formulary, in Quesenberry & Carpenter (eds), Ferrets, Rabbits and Rodents 4th ed, 2021:620-630 - so Carpenter and FRR are one chain, not two sources.
· Carpenter's Exotic Animal Formulary, 6th Ed — Carpenter's Exotic Animal Formulary 6th ed, Table 10.1 (Antimicrobial Agents Used in Rabbits.a). — Carpenter's Exotic Animal Formulary 6th ed, Table 10.1 (Antimicrobial Agents Used in Rabbits.a).
· Carpenter's Exotic Animal Formulary, 6th ed, Table 9.1 (Antimicrobial and Antifungal Agents Used in Rodents): 'Cephalexin 25 mg/kg SC q24h130 | Hamsters, gerbils'. NOTE: the previously named primary (Morrisey JK, Carpenter JW. Formulary. In: Quesenberry KE, Carpenter JW, eds. Ferrets, Rabbits, and Rodents, 4th ed., 2021:620-630) prints q12h, NOT q24h, for this species and route, and does not support the served frequency. The two held books disagree on the interval and the frequency field is deliberately NOT changed.
· Flecknell PA. Analgesia and post-operative care. Laboratory Animal Anaesthesia; 2016:141-192. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.771 — Carpenter's Exotic Animal Formulary 6th ed, Table 9.1 (Antimicrobial and Antifungal Agents Used in Rodents.a).
· 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. — Plumb's 10th ed printed p.234, Cephalexin monograph spanning p.234-236.
· Morrisey JK, Carpenter JW, et al. Formulary. In: Quesenberry KE, Orcutt CJ, Mans C, et al. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, 4th ed., Elsevier, St. Louis, MO; 2021:620-630. | Ness RD, Johnson-Delaney C. Sugar gliders. In: Quesenberry KE, Carpenter JW, eds. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, 3rd ed., Saunders/Elsevier, St. Louis, MO; 2012:393-410. | Pye GW, Carpenter JW. A guide to medicine and surgery in sugar gliders. Vet Med. 1999;94:891-905. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.703 — Carpenter's Exotic Animal Formulary 6th ed, Table 7.1 (Antimicrobial and Antifungal Agents Used in Sugar Gliders).
· Morrisey JK, Carpenter JW, et al. Formulary. In: Quesenberry KE, OrcuttCJ, Mans C, et al. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, 4th ed., Elsevier, St. Louis, MO; 2021:620-630. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.931 — Carpenter's Exotic Animal Formulary 6th ed, Table 11.1 (Antimicrobial Agents Used in Ferrets).
· Morrisey JK, Carpenter JW. Formulary. In: Quesenberry KE, Carpenter JW, eds. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, 4th ed., Elsevier, St. Louis, MO; 2021:620-630. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.771 — PRINTED DETAIL MISSING FROM THIS RULE (retrieved 2026-08-19): Although cephalexin has been used in some small mammal species, products licensed in the United Kingdom state: Do not use in rabbits, guinea pigs, hamsters and gerbils, and other small rodents; potentially serious enterocolitis can result. — Plumb's 10th ed, printed p.235. Currently in internal_notes, which the migration that created it states is "deliberately NOT added to any response schema" — so no clinician has ever seen it.
· Papich MG. Saunders Handbook of Veterinary Drugs, 5th ed — Cephalexin, Small Animal Dosage, printed p.144: "Dogs • Pyoderma and other skin infections: 22-25 mg/kg q12h PO. For other infections: 10-30 mg/kg q6-12h PO." Corroborating: BSAVA Small Animal Formulary, 10th ed, Part A, Cefalexin, printed p.68: "Dogs: 15 mg/kg p.o. q8-12h. Increased doses (20-30mg/kg p.o. q8-12h) should be used for […]" — EDITION CORRECTED 2026-08-07: this citation named the 5th edition, which is not held. The page locator resolves in the 4th ed (2016), the copy actually consulted, and that page names the drug; the reference is to the 4th.
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.234, Cephalexin monograph spanning p.234-236.
· Plumb's Veterinary Drug Handbook, 10th ed (2023), 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 — Plumb's 10th ed printed p.236, Cephalexin monograph spanning p.234-236.
· 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. doi:10.1016/j.tvjl.2019.02.008 — Plumb's 10th ed printed p.234, Cephalexin monograph spanning p.234-236.
Cephalexin (Keflex) Dosage for Rabbits, Ferrets | ExoticRx