Which species have cited Nafcillin dosing data?

Nafcillin dosing in the ExoticRx formulary covers 2 species: Cat (Domestic), Dog (Domestic).

Is Nafcillin a controlled substance?

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

What are the side effects of Nafcillin?

Reported side effects, adverse reactions, and contraindications for Nafcillin: Phlebitis at IV site. Hepatotoxicity possible. Interstitial nephritis rare. Do not use for MRSA.

Nafcillin

US brand names:Nallpen

Calculate dosage

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.

Nafcillin is dosed at 10–22 mg/kg IV q6-8h in dogs, per Plumb's Veterinary Drug Handbook, 9th Ed. Verify against current literature before clinical use.

Drug Class

Antibiotic

Routes

IVIM

Indications

Staphylococcal infectionsStaphylococcal infections (methicillin-sensitive)

Mechanism of Action

Binds PBPs inhibiting cell wall synthesis. Resistant to staphylococcal penicillinase. Narrow gram-positive spectrum.

Side effects & warnings

Phlebitis at IV site. Hepatotoxicity possible. Interstitial nephritis rare. Do not use for MRSA.

Species with Nafcillin dosing data (2 dose rules)

Cat (Domestic)Dog (Domestic)

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

Evidence levels across 2 dose rules

Moderate×1Weak×1

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

Backed by a published source

· Plumb's Veterinary Drug Handbook, 9th Ed

Sample dosing (2 of 2 cited rules)

A dog/cat sample is shown here. Cited dosing for all 2 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)	IV	10–22 mg/kg	q6-8h	Moderate	Plumb's Veterinary Drug Handbook, 9th Ed
Cat (Domestic)	IV	10–22 mg/kg	q6-8h	Weak	Plumb's Veterinary Drug Handbook, 9th Ed

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