Which species have cited Penicillin G dosing data?

Penicillin G dosing in the ExoticRx formulary covers 4 species: Cat (Domestic), Dog (Domestic), Goat (Caprine), Sheep (Ovine).

Is Penicillin G a controlled substance?

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

Penicillin G

US brand names:Pen-G, Crysticillin

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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.

Penicillin G is dosed at 13.2–26.4 mg/kg IM q12-24h in dogs, per Plumb's Veterinary Drug Handbook, 9th Ed. Verify against current literature before clinical use.

Drug Class

Antibiotic

Routes

IMIVSC

Indications

Bacterial infectionsblacklegfoot rotGram-positive infectionsleptospirosis (procaine)listeriosis

Mechanism of Action

Inhibits bacterial cell wall synthesis by binding PBPs. Bactericidal. Narrow spectrum: primarily gram-positive and some anaerobes.

Side effects & warnings

CONTRAINDICATED in rabbits, guinea pigs, hamsters. Hypersensitivity reactions. Procaine form: IM/SC only (never IV). Potassium form: slow IV only. Pain at injection site.

Species with Penicillin G dosing data (4 dose rules)

Cat (Domestic)Dog (Domestic)Goat (Caprine)Sheep (Ovine)

Species references:All Cat (Domestic) drugs All Dog (Domestic) drugs All Goat (Caprine) drugs All Sheep (Ovine) drugs

Evidence levels across 4 dose rules

Strong×2Moderate×2

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

Backed by 3 published sources

· FARAD Withdrawal Guidelines
· Plumb's Veterinary Drug Handbook
· Plumb's Veterinary Drug Handbook, 9th Ed

Sample dosing (2 of 4 cited rules)

A dog/cat sample is shown here. Cited dosing for all 4 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)	IM	13.2–26.4 mg/kg	q12-24h	Strong	Plumb's Veterinary Drug Handbook, 9th Ed
Cat (Domestic)	IM	13.2–26.4 mg/kg	q12-24h	Strong	Plumb's Veterinary Drug Handbook, 9th Ed

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