Dogs & CatsSource: Trepanier 2003
Orthopedic surgery: 20 mg/kg IV at induction, then every 90 min until wound closure
Antibiotic Therapy
Cefazolin
First-generation (injectable) cephalosporin · bactericidal (cell-wall synthesis inhibitor)
Species: Dogs & Cats11 dose protocols3 dosage forms
This page is a calculation and educational reference for veterinarians and veterinary students. It does not replace examination, culture and susceptibility testing, clinical judgment, or the attending veterinarian's final decision.
Drug overview
First-generation (injectable) cephalosporin · bactericidal (cell-wall synthesis inhibitor)
Brand names: Ancef®, Kefzol®, Zolicef®
General systemic dose: 20–25 mg/kg parenteral · every 8 hSource: Plumb's (general)
Spectrum of activity
A first-generation, bactericidal cephalosporin that is injectable only (no oral absorption). It has excellent Gram-positive cover and — unlike the penicillins — is active against beta-lactamase-producing staphylococci (S. aureus, S. pseudintermedius) as well as streptococci, Corynebacterium and Trueperella. It covers most anaerobes except Bacteroides fragilis, and is active against some susceptible aerobic Gram-negatives (E. coli, Klebsiella, Proteus mirabilis, Pasteurella, Haemophilus). But it is intrinsically inactive against: enterococci, Listeria, MRSA/MRSP, Pseudomonas, Enterobacter, Serratia, Citrobacter, indole-positive Proteus, and cell-wall-free/intracellular bacteria (Mycoplasma, Rickettsia).
Veterinary uses and doses
Surgical prophylaxis
Dogs & CatsSource: Trepanier 2003
Soft-tissue surgery: 20 mg/kg IV during surgery, then one 20 mg/kg SC dose 6 hours later
DogSource: Greene 1998
Alternative timing: 8 mg/kg IV immediately before and during surgery, 1 hour apart
Systemic infection
DogSource: Greene 1998
5–25 mg/kg IM or IV · every 6–8 h
CatSource: Greene 1998
Cat: 33 mg/kg IV or IM · every 8–12 h
CatSource: Lappin 2002
Cat: 20–25 mg/kg IM or IV · every 8 h
Orthopedic infection
DogSource: Greene 1998
22 mg/kg IV, IM or SC · every 6–8 h · up to 7 days
Sepsis / bacteremia
DogSource: Greene 1998 / Hardie 2000
15–25 mg/kg IV, IM or SC · every 4–8 h · up to 7 days
CatSource: Hardie 2000
Cat: 20–25 mg/kg IV · every 4–8 h
Neonatal sepsis
DogSource: Kampschmidt 2006
Neonate: 10–30 mg/kg IV or IO · every 8 h
CatSource: Kampschmidt 2006
Neonatal cat: 10–30 mg/kg IV or IO · every 8 h
Dosage forms
- Vial 500 mg
- Vial 1000 mg (1 g)
- Vial 250 mg
Safety and clinical notes
- Cefazolin has no oral absorption and is injectable only (IV/IM/SC); for oral therapy use an oral cephalosporin (e.g. cephalexin).
- It is first-generation: excellent Gram-positive cover and — unlike the penicillins — active against beta-lactamase-producing staphylococci; but intrinsically inactive against enterococci, Listeria, MRSA/MRSP, Pseudomonas, Enterobacter, Serratia and Citrobacter.
- Active against most anaerobes except Bacteroides fragilis.
- IM injection may be painful (less than other cephalosporins); give IV slowly over 3–5 minutes (rapid high-dose injection may cause seizures).
- Contraindicated in cephalosporin allergy; cross-reactivity with penicillins and carbapenems is possible.
- Dose reduction may be needed in renal impairment; use with caution alongside nephrotoxic drugs (aminoglycosides, amphotericin B).
- It is incompatible in one syringe/solution with aminoglycosides (amikacin, kanamycin) and several other drugs; compatible with normal saline, Ringer's and metronidazole.
- The reconstituted solution is stable for up to 24 hours at room temperature and up to 96 hours refrigerated (protect from light).
- Considered relatively safe in pregnancy (class B); use with caution during lactation (may alter the neonate's gut flora).
Cited sources
- Plumb's (general)
- Trepanier 2003
- Greene 1998
- Lappin 2002
- Greene 1998 / Hardie 2000
- Hardie 2000
- Kampschmidt 2006
Calculate a weight-based dose
Drug-data last updated: