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.
Ampicillin is dosed at 5–30 mg/kg SC, IM, IV q8-12h in ferrets, per Brown SA. Ferrets. In: Jenkins JR, Brown SA, eds. A Practitioner's Guide to Rabbits and Ferrets; American Animal Hospital Association, Lakewood, CO; 1993:43-111. — 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). Verify against current literature before clinical use.
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins. Broader spectrum than penicillin G with gram-negative coverage.
Side effects & warnings
CONTRAINDICATED in rabbits, guinea pigs, and hamsters (fatal dysbiosis). May cause GI upset. Cross-reactivity with other beta-lactams. IM injection may be painful.
Species with Ampicillin dosing data (36 dose rules)
Each ExoticRx dose rule is graded by the strength of its primary evidence — see the editorial process.
Sample dosing (2 of 36 cited rules)
A dog/cat sample is shown here. Cited dosing for all 29 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 10th ed printed p.78, Ampicillin monograph spanning p.78-81.Compilation only — we have not located an independent source that prints this figure.
Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.78, Ampicillin monograph spanning p.78-81. — Plumb's 10th ed printed p.79, Ampicillin monograph.Compilation only — we have not located an independent source that prints this figure.
· 122. Meredith A. BSAVA Small Animal Formulary: Part B: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, Gloucester, UK; 2015. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.770 — Carpenter's Exotic Animal Formulary 6th ed, Table 9.1 (Antimicrobial and Antifungal Agents Used in Rodents.a).
· 148. Jenkins JR. Husbandry and diseases of old world chameleons. J Small Exot Anim Med. 1992;1:166-171. — Source: Mader's Reptile and Amphibian Medicine and Surgery, 3rd Ed, p.1401
· 184. Hedley J. BSAVA Small Animal Formulary: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, UK; 2020. / 243. Klaphake E, Gibbons PM, Sladky KK, et al. Reptiles. In: Carpenter JW, eds. Exotic Animal Formulary, 5th ed., Elsevier, St. Louis, MO; 2018:81-166. — 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).
·
Upgrade for Full Details
Upgrade to Pro or Student to unlock the full dose ranges and frequency for every species. The drug's mechanism, warnings, indications, and cited sources are free to read.
184. Hedley J. BSAVA Small Animal Formulary: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, UK; 2020. || 243. Klaphake E, Gibbons PM, Sladky KK, et al. Reptiles. In: Carpenter JW, eds. Exotic Animal Formulary, 5th ed., Elsevier, St. Louis, MO; 2018:81-166. — 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).
· 207. De Herdt P, Devriese LA, De Groote B, et al. Antibiotic treatment of Streptococcus bovis infections in pigeons. Proc Eur Conf Avian Med Surg; 1993:297-304. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.406 doi:10.1080/03079459308418947 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· 207. De Herdt P, Devriese LA, De Groote B, et al. Antibiotic treatment of Streptococcus bovis infections in pigeons. Proc Eur Conf Avian Med Surg; 1993:297-304. — 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).
· 239. Dorrestein GM. Infectious diseases and their therapy in Passeriformes Antimicrobial Therapy in Caged Birds and Exotic Pets, Veterinary Learning Systems, Trenton, NJ; 1995:11-27. — 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).
· 260. Ensley PK, Janssen DL. A preliminary study comparing the pharmacokinetics of ampicillin given orally and intramuscularly to psittacines: Amazon parrots (Amazona spp.) and blue-naped parrots (Tanygnathus lucionensis). J Zoo Anim Med. 1981;12:42- 47. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.406 doi:10.2307/20094514 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.1 (Antimicrobial Agents Used in Birds.a).
· 297. Schumacher J. Respiratory medicine of reptiles. Vet Clin North Am Exot Anim Pract. 2011;14:207-224. — Source: Mader's Reptile and Amphibian Medicine and Surgery, 3rd Ed, p.1401
· 5. Greenacre, C.B., Luna, G.L., and Morishita, T.M. (2018). Backyard poultry and waterfowl. In: Exotic Animal Formulary, 5e (ed. J.W. Carpenter), 377-432. St. Louis, Missouri: Elsevier. — Source: Greenacre & Morishita, Backyard Poultry Medicine and Surgery, 2nd Ed, p.588
· Brown SA. Ferrets. In: Jenkins JR, Brown SA, eds. A Practitioner's Guide to Rabbits and Ferrets; American Animal Hospital Association, Lakewood, CO; 1993:43-111. — 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).
· Carpenter's Exotic Animal Formulary, 6th Ed — Carpenter's Exotic Animal Formulary, 6th ed, Table 5.1. NOTE: the served figure was matched against the table as a whole, not against this drug's own row, so confirm the number on the page before relying on it.
· Greenacre, C.B., Luna, G.L., and Morishita, T.M. (2018). Backyard poultry and waterfowl. In: Exotic Animal Formulary, 5e (ed. J.W. Carpenter), 377-432. St. Louis, Missouri: Elsevier. — Source: Greenacre & Morishita, Backyard Poultry Medicine and Surgery, 2nd Ed, p.588
· 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.407 — 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. (co-cited: Klaphake E, Gibbons PM, Sladky KK, et al. Reptiles. In: Carpenter JW, eds. Exotic Animal Formulary, 5th ed., Elsevier, St. Louis, MO; 2018:81-166.) — 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).
· Hedley J. BSAVA Small Animal Formulary: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, UK; 2020. | Klaphake E, Gibbons PM, Sladky KK, et al. Reptiles. In: Carpenter JW, eds. Exotic Animal Formulary, 5th ed., Elsevier, St. Louis, MO; 2018:81-166. — 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).
· 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).
· MacDonald K. Infective endocarditis in dogs: diagnosis and therapy. Vet Clin North Am Small Anim Pract. 2010;40:665-684. doi:10.1016/j.cvsm.2010.03.010 — Plumb's 10th ed printed p.78, Ampicillin monograph spanning p.78-81.
· Meredith A. BSAVA Small Animal Formulary: Part B: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, Gloucester, UK; 2015. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.770 — Carpenter's Exotic Animal Formulary 6th ed, Table 9.1 (Antimicrobial and Antifungal Agents Used in Rodents.a).
· Plumb's 10th ed printed p.78, Ampicillin monograph spanning p.78-81.
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Ampicillin, Dosages, CATTLE, Polyflex label dosage, printed p. 80; corroborated by Papich Handbook of Veterinary Drugs, 5th Ed, 'Cattle and Calves — Ampicillin Trihydrate: 4.4 to 11 mg/kg q24h IM', printed p. 45 — 21 CFR § 522.90b (Ampicillin trihydrate powder for injection), conditions of use for Cattle: 4.4092-11.0231 mg/kg (the regulation prints this per pound; converted at 2.2046226 lb/kg). Related tolerances: 21 CFR § 556.40. Retrieved from the eCFR API, snapshot 2026-01-01. https://www.ecfr.gov/current/title-21/section-522.90b — 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.
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.78, Ampicillin monograph spanning p.78-81. — Plumb's 10th ed printed p.79, Ampicillin monograph.
· Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.78, Ampicillin monograph spanning p.78-81. — Plumb's 10th ed printed p.80, Ampicillin monograph. — 21 CFR § 522.90a (Ampicillin trihydrate suspension), conditions of use for Swine: 6.6139-6.6139 mg/kg (the regulation prints this per pound; converted at 2.2046226 lb/kg). Related tolerances: 21 CFR § 556.40. Retrieved from the eCFR API, snapshot 2026-01-01. https://www.ecfr.gov/current/title-21/section-522.90a
· Ramsey I, ed. BSAVA Small Animal Formulary, 10th ed. Part B: Exotic Pets. Gloucester: British Small Animal Veterinary Association; 2023. p.23.
· Schumacher J. Respiratory medicine of reptiles. Vet Clin North Am Exot Anim Pract. 2011;14:207-224. — Source: Mader's Reptile and Amphibian Medicine and Surgery, 3rd Ed, p.1401
· Spörle H, Gobel T, Schildger B. Blood levels of some anti-infectives in the spur-thighed tortoise (Testudo hermanni). Proc 4th Intl Colloq Path Med Rept Amph; 1991:120-128. — Carpenter's Exotic Animal Formulary 6th ed, Table 4.1 (Antimicrobial Agents Used in Reptiles.a,b).
· Spörle H, Gobel T, Schildger B. Blood levels of some anti-infectives in the spur-thighed tortoise (Testudo hermanni). Proc 4th Intl Colloq Path Med Rept Amph; 1991:120-128. — 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).