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.
Amoxicillin is dosed at 10–20 mg/kg PO q12h in ferrets, per Hillyer EV, Brown SA. Ferrets. In: Birchard SJ, Sherding RG, eds. Saunders Manual of Small Animal Practice; WB Saunders, Philadelphia, PA; 1994:1317-1344. — Carpenter's Exotic Animal Formulary 6th ed, Table 11.1 (Antimicrobial Agents Used in Ferrets). 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 48 cited rules)
A dog/cat sample is shown here. Cited dosing for all 27 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.
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. Distributed by John Wiley & Sons, Inc. doi:10.1016/j.tvjl.2019.02.008 — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69.
· 107. Divers SJ. Empirical doses of antimicrobial drugs commonly used in reptiles. Exot DVM. 1998;1:23. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.212 — Carpenter's Exotic Animal Formulary 6th ed, Table 4.1 (Antimicrobial Agents Used in Reptiles.a,b).
· 167. National Office for Animal Health (NOAH). Antibiotics for animals. Available at: http://www.noah.co.uk/medicine-topics/antibiotics-for-animals. Accessed August 13, 2020. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.617 — Carpenter's Exotic Animal Formulary 6th ed, Table 6.1 (Antimicrobial Agents Used in Backyard Poultry, Gamebirds, and Waterfowl.a,b).
· 177. Coles BH. Prescribing for exotic birds. In: Bishop Y, eds. The Veterinary Formulary, 5th ed., Pharmaceutical Press, London, UK; 2001:99-105. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.405 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
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Compilation only — we have not located an independent source that prints this figure.
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184. Hedley J. BSAVA Small Animal Formulary: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, UK; 2020. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.212 — Carpenter's Exotic Animal Formulary 6th ed, Table 4.1 (Antimicrobial Agents Used in Reptiles.a,b).
· 21 CFR 522.88(d)(2) (Amoxicillin), approved conditions of use for Cattle: 3 to 5 mg per pound of body weight daily for up to 5 days by intramuscular or subcutaneous injection (= 6.614-11.023 mg/kg; converted at 2.2046226 lb/kg). Indications as approved: respiratory tract infections (shipping fever, pneumonia) and acute necrotic pododermatitis (foot rot). Related tolerances: 21 CFR 556.38. Retrieved from the eCFR renderer API 2026-08-12. https://www.ecfr.gov/current/title-21/section-522.88
· 236. Dorrestein GM. Studies on Pharmacokinetics of Some Antibacterial Agents in Homing Pigeons (Columba livia), Thesis: Utrecht University; 1986. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.405 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· 245. Dorrestein GM, Van Gogh H, Rinzema JD, et al. Comparative study of ampicillin and amoxicillin after intravenous, intramuscular and oral administration in homing pigeons (Columba livia). Res Vet Sci. 1987;42:343-348. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.405 doi:10.1016/s0034-5288(18)30716-1 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· 29. Isenbügel E, Baumgartner R. Diseases of the hedgehog. In: Fowler M, eds. Zoo and Wild Animal Medicine: Current Therapy, 3rd ed., WB Saunders, Philadelphia, PA; 1993:294-302. | 45. Lightfoot T. Therapeutics of African pygmy hedgehogs and prairie dogs. Vet Clin North Am Exot Anim Pract. 2000;3:155-172 doi:10.1016/s1094-9194(17)30099-3. | 68. Smith A. General husbandry and medical care of hedgehogs. In: Bonagura JD, eds. Kirk's Current Veterinary Therapy XIII: Small Animal Practice; WB Saunders, Philadelphia, PA; 2000:1128-1133. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.732 — Carpenter's Exotic Animal Formulary 6th ed, Table 8.1 (Antimicrobial Agents Used in Hedgehogs).
· 68. Elviss NC, Williams LK, Jørgensen F, et al. Amoxicillin therapy of poultry flocks: effect upon the selection of amoxicillin-resistant commensal Campylobacter spp. J Antimicrob Chemother. 2009;64:702-711 doi:10.1093/jac/dkp277. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.617 — Carpenter's Exotic Animal Formulary 6th ed, Table 6.1 (Antimicrobial Agents Used in Backyard Poultry, Gamebirds, and Waterfowl.a,b).
· 70. Divers SJ. Empirical doses of antimicrobial drugs commonly used in reptiles. Exot DVM. 1998;1:23. | 88. Frye FL. Reptile Care: An Atlas of Diseases and Treatments. Neptune City, NJ: TFH Publications, Inc; 1991:1-637. — Source: Mader's Reptile and Amphibian Medicine and Surgery, 3rd Ed, p.1401
· 793. Rupley AE. Critical care of pet birds. Vet Clin North Am Exot Anim Pract. 1998;1:11-41. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.405 doi:10.1016/S1094-9194(17)30153-6 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· 802. Samour J. Pharmaceutics commonly used in avian medicine. In: Samour J, eds. Avian Medicine; Mosby, Philadelphia, PA; 2000:388-418. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.405 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· Coles BH. Prescribing for exotic birds. In: Bishop Y, eds. The Veterinary Formulary, 5th ed., Pharmaceutical Press, London, UK; 2001:99-105.; Rupley AE. Critical care of pet birds. Vet Clin North Am Exot Anim Pract. 1998;1:11- 41. doi:10.1016/S1094-9194(17)30153-6 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· Divers SJ. Empirical doses of antimicrobial drugs commonly used in reptiles. Exot DVM. 1998;1:23. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.212 — Carpenter's Exotic Animal Formulary 6th ed, Table 4.1 (Antimicrobial Agents Used in Reptiles.a,b).
· Divers SJ. Empirical doses of antimicrobial drugs commonly used in reptiles. Exot DVM. 1998;1:23.; Hedley J. BSAVA Small Animal Formulary: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, UK; 2020. — Carpenter's Exotic Animal Formulary 6th ed, Table 4.1 (Antimicrobial Agents Used in Reptiles.a,b).
· Elviss NC, Williams LK, Jørgensen F, et al. Amoxicillin therapy of poultry flocks: effect upon the selection of amoxicillin-resistant commensal Campylobacter spp. J Antimicrob Chemother. 2009;64:702-711. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.617 doi:10.1093/jac/dkp277 — Carpenter's Exotic Animal Formulary 6th ed, Table 6.1 (Antimicrobial Agents Used in Backyard Poultry, Gamebirds, and Waterfowl.a,b).
· FARAD Withdrawal Guidelines [2026-08-05: FARAD (Food Animal Residue Avoidance Databank, https://www.farad.org/) publishes meat/milk WITHDRAWAL intervals for extralabel use — it is not a dosing authority. This dose could not be corroborated in Plumb's 10th ed for this species, unlike the other 15 FARAD-cited rules. Needs a product label or primary reference before it can be considered sourced.]
· Haneveld-v Laarhoven MA, Dorrestein GM. IME-sudden high mortality in canaries. J Assoc Avian Vet. 1990;4:82. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.406 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· Hedley J. BSAVA Small Animal Formulary: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, UK; 2020. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.212 — Carpenter's Exotic Animal Formulary 6th ed, Table 4.1 (Antimicrobial Agents Used in Reptiles.a,b).
· Hillyer EV, Brown SA. Ferrets. In: Birchard SJ, Sherding RG, eds. Saunders Manual of Small Animal Practice; WB Saunders, Philadelphia, PA; 1994:1317-1344. — Carpenter's Exotic Animal Formulary 6th ed, Table 11.1 (Antimicrobial Agents Used in Ferrets).
· ISCAID UTI Guidelines; Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.69, Amoxicillin monograph spanning p.67-69.
· Leib MS. Helicobacter Gastritis: Does it Cause Vomiting in Dogs and Cats? In: Western States Veterinary Conference Proceedings; 2012. — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69.
· 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. — Carpenter's Exotic Animal Formulary 6th ed, Table 7.1 (Antimicrobial and Antifungal Agents Used in Sugar Gliders).
· Papich/Saunders Handbook of Veterinary Drugs, 4th Ed, p.39 — 21 CFR § 522.88 (Amoxicillin), conditions of use for Cattle: 6.6139-11.0231 mg/kg (the regulation prints this per pound; converted at 2.2046226 lb/kg). Related tolerances: 21 CFR § 556.38. Retrieved from the eCFR API, snapshot 2026-01-01. https://www.ecfr.gov/current/title-21/section-522.88
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69.
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69. — Plumb's 10th ed printed p.69, Amoxicillin monograph. | ORIGINAL SOURCE THE BOOK CITES (2026-08-20): the dose row carries superscript 9 — "20 mg/kg PO every 8 hours9 Use ammonium chloride with caution in pa" — which resolves in the monograph's own reference list to: Benson KK, Quimby JM, Dowers KL, et al. Pilot study of side effects and serum and urine concentrations of amoxicillin-clavulanic acid in azotemic and non-azotemic cats. Journal of Feline Medicine & Surgery. 2019;22(8):729-735. This records what the handbook attributes the figure to. It is NOT a statement that the reference was read or that it validates the dose.
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69. — Plumb's 10th ed printed p.69, Amoxicillin monograph. — Plumb's Veterinary Drug Handbook, 10th ed, Amoxicillin monograph, printed p.69, CATS: "Systemic infections (extra-label): 11 - 22 mg/kg PO every 8 hours."
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69. — Plumb's 10th ed printed p.69, Amoxicillin monograph. — Plumb's Veterinary Drug Handbook, 10th ed, Amoxicillin monograph, printed p.69, CATS: "Systemic infections (extra-label): 11 - 22 mg/kg PO every 8 hours; duration of treatment should be […]"
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69. — Plumb's Veterinary Drug Handbook, 10th ed, Amoxicillin monograph, printed p.69, DOGS: "Systemic infections (extra-label): 11 - 22 mg/kg PO every 8 hours." Corroborated: Papich MG, Saunders Handbook of Veterinary Drugs, 4th ed, printed p.39: "Dogs and Cats • 6.6-20 mg/kg q8-12h PO"; BSAVA Small Animal Formulary, 10th ed, Part A: "Oral: 10 mg/kg p.o. q8-12h."
· Plumb's Veterinary Drug Handbook, 10th ed (2023), Amoxicillin, printed p.69
· Plumb's Veterinary Drug Handbook, 10th ed (2023), Amoxicillin, printed p.69 — Plumb's Veterinary Drug Handbook, 10th ed, Amoxicillin monograph, printed p.69, DOGS: "Borreliosis (Lyme disease) (extra-label): 20 mg/kg PO 3 times daily for 30 days."
· Plumb's Veterinary Drug Handbook, 10th ed (2023), p.96, DOGS — 'Systemic infections (extra-label): 11 - 22 mg/kg PO every 8 hours' — Plumb's 10th ed printed p.69, Amoxicillin monograph spanning p.67-69.
· Ramsey I, ed. BSAVA Small Animal Formulary, 10th ed. Part B: Exotic Pets. Gloucester: British Small Animal Veterinary Association; 2023. p.20.
· Visser C, Wijnbergen A, Bleich A. Maeuse und ratten. In: Fehr M, Sassenburg L, Zwart P, eds. Krankheiten der Heimtiere, Schluetersche Verlagsgesellschaft, Hannover, Germany; 2015. — Carpenter's Exotic Animal Formulary 6th ed, Table 9.1 (Antimicrobial and Antifungal Agents Used in Rodents.a).
· 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. Distributed by John Wiley & Sons, Inc. doi:10.1016/j.tvjl.2019.02.008 — Plumb's 10th ed printed p.67, Amoxicillin monograph spanning p.67-69.
Chinchilla Drug Dosing: A Vet Reference
Antibiotic, analgesic, anesthetic, and dental-disease dosing for Chinchilla lanigera. Same dysbiosis warnings as rabbits, plus the chinchilla-specific sensitivities to anesthesia and stress that change post-op care.