Cefazolin Sodium

Cephalosporin antibiotic First-generation cephalosporin

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog IV or IM 20-25 mg/kg q8h Duration: Varies with infection; typically 5-7 days
Notes: For surgical prophylaxis: administer 20 mg/kg IV at induction, repeat every 90 minutes during surgery if needed.
Cat IV or IM 20-25 mg/kg q8h Duration: Varies with infection; typically 5-7 days
Notes: For surgical prophylaxis: administer 20 mg/kg IV at induction, repeat every 90 minutes during surgery if needed.
Horse IV or IM 10-20 mg/kg q6-8h Duration: Varies with infection; typically 5-7 days
Notes: For surgical prophylaxis: administer 10-20 mg/kg IV at induction, repeat every 2 hours during surgery if needed.
Cattle IV or IM 10-20 mg/kg q8-12h Duration: Varies with infection; typically 3-5 days
Notes: Not commonly used in cattle; consider withdrawal times. For surgical prophylaxis: administer 10-20 mg/kg IV at induction.
Small Ruminants (sheep, goats) IV or IM 10-20 mg/kg q8-12h Duration: Varies with infection; typically 3-5 days
Notes: Not commonly used in food animals; consider withdrawal times.
Rabbit IV or IM 20 mg/kg q8-12h Duration: Varies with infection; typically 5-7 days
Notes: Use cautiously in rabbits due to potential GI disturbances.
Birds/Poultry IM 50-100 mg/kg q8-12h Duration: Varies with infection; typically 3-5 days
Notes: Not commonly used in poultry; consider withdrawal times.
Exotic/Other (reptiles, small mammals) IM or IV 20-50 mg/kg q12-24h Duration: Varies with infection
Notes: Dose based on species and clinical judgment; off-label use.

Clinical Indications & Species Uses

General Indications
  • Perioperative prophylaxis for surgical procedures to reduce the risk of surgical site infections.
Dog (Canine)
  • Treatment of susceptible bacterial infections: skin and soft tissue infections, urinary tract infections, respiratory tract infections, bone and joint infections, septicemia, and surgical prophylaxis.
Cat (Feline)
  • Treatment of susceptible bacterial infections: skin and soft tissue infections, urinary tract infections, respiratory tract infections, and surgical prophylaxis.
Horse (Equine)
  • Treatment of susceptible bacterial infections: respiratory tract infections, skin and soft tissue infections, septic arthritis, and surgical prophylaxis.
Rabbit & Small Mammals
  • Treatment of susceptible bacterial infections: respiratory tract infections, skin infections, and surgical prophylaxis.
Exotic & Other Species
  • Treatment of susceptible bacterial infections in reptiles, small mammals, and other exotic species (off-label use).

Pharmacology & Mechanism of Action

Drug Class: Cephalosporin antibiotic | Pharmacological Group: First-generation cephalosporin

Mechanism of Action: Cefazolin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), thereby disrupting peptidoglycan cross-linking. This leads to cell wall weakening, osmotic instability, and ultimately bacterial lysis. It is bactericidal against susceptible organisms.

Pharmacodynamics: Cefazolin exhibits time-dependent killing, with efficacy correlated with the duration of time that serum concentrations exceed the minimum inhibitory concentration (MIC) of the pathogen. It is active against many gram-positive cocci (e.g., Staphylococcus spp., Streptococcus spp.) and some gram-negative organisms (e.g., Escherichia coli, Klebsiella spp.). It is not effective against methicillin-resistant staphylococci, Enterococcus spp., Pseudomonas aeruginosa, or anaerobes like Bacteroides fragilis.

⚑ Pharmacokinetics Summary

Absorption: Cefazolin is poorly absorbed orally; therefore, it is administered parenterally (IV or IM). After IM injection, peak plasma concentrations are achieved within 1-2 hours.
Distribution: Cefazolin is widely distributed into body tissues and fluids, including synovial fluid, pleural fluid, and bone. It penetrates the blood-brain barrier poorly unless the meninges are inflamed. It crosses the placenta and is excreted in milk in low concentrations.
Metabolism: Cefazolin undergoes minimal hepatic metabolism; it is primarily eliminated unchanged by the kidneys.
Excretion: Cefazolin is excreted predominantly via glomerular filtration and tubular secretion in the urine. In animals with normal renal function, approximately 80-100% of the dose is recovered in urine within 24 hours.
Half-Life: Dogs: 1-2 hours; Cats: 1-2 hours; Horses: 1-2 hours; Cattle: 1-2 hours; Rabbits: 1-2 hours; Birds: 1-2 hours (approximate).
Bioavailability: Oral bioavailability is negligible; therefore, it is administered parenterally. IM absorption is rapid and complete.
Protein Binding: Cefazolin is approximately 80% protein-bound in dogs and cats, and about 70-80% in horses.

Available Formulations & Strengths

Injectable Solution (powder for reconstitution) 500 mg, 1 g, 5 g, 10 g vials (IV or IM)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to cephalosporins or other beta-lactam antibiotics.
  • History of anaphylactic reactions to penicillins (cross-reactivity possible).
  • Use in animals with severe renal impairment without dose adjustment.
Warnings & Clinical Precautions:
  • Use with caution in animals with a history of allergic reactions to penicillins or other cephalosporins.
  • Dose adjustment may be necessary in animals with renal insufficiency.
  • Prolonged use may result in overgrowth of non-susceptible organisms (e.g., Candida, Clostridium difficile).
  • In food animals, observe withdrawal times to avoid violative residues.
  • Intramuscular injections may cause pain and tissue irritation; administer deeply into a large muscle mass.
  • Rapid IV administration may cause nausea, vomiting, or hypotension; infuse slowly.

Adverse Effects & Reactions

Common:

  • Pain at injection site
  • Swelling at injection site
  • Gastrointestinal upset (nausea, vomiting, diarrhea) in some species

Serious / Severe:

  • Anaphylaxis (rare but potentially fatal)
  • Acute renal injury (especially with high doses or in dehydrated animals)
  • Clostridium difficile-associated diarrhea (prolonged use)
  • Seizures (with very high doses or in renal failure)

Rare:

  • Blood dyscrasias (neutropenia, thrombocytopenia)
  • Hepatotoxicity
  • Interstitial nephritis
  • Superinfections

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Aminoglycosides (e.g., gentamicin, amikacin) Additive nephrotoxicity; increased risk of renal damage. High
Loop diuretics (e.g., furosemide) Increased risk of nephrotoxicity. Moderate
Probenecid Decreases renal tubular secretion of cefazolin, increasing its serum concentration and duration of action. Moderate
Warfarin and other anticoagulants Cephalosporins may enhance the effect of anticoagulants by interfering with vitamin K metabolism. Moderate
Bacteriostatic antibiotics (e.g., tetracyclines, macrolides) Potential antagonism of bactericidal activity; avoid concurrent use. Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Seizures
  • Neurological signs (muscle twitching, tremors)
  • Nausea and vomiting
  • Diarrhea
  • Acute renal failure (with very high doses)

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. In cases of recent oral ingestion (though rare), consider gastric lavage or activated charcoal. For parenteral overdose, monitor renal function and provide fluid therapy to enhance elimination. In severe cases, hemodialysis may be considered. Anticonvulsants (e.g., diazepam) may be used to control seizures.

Food Animal Withdrawal Times

πŸ₯© Meat: 4 daysπŸ₯› Milk: 96 days

Withdrawal times are not established for all species; consult regulatory guidelines. For cattle, meat withdrawal is 4 days and milk withdrawal is 96 hours. For sheep and goats, withdrawal times may vary; use extra-label with caution. Not approved for use in poultry in the US.

Storage, Handling & Regulatory Information

Storage Temperature: Store powder at room temperature (20-25Β°C). Reconstituted solution is stable for 24 hours at room temperature and 96 hours under refrigeration (2-8Β°C).

Handling & Special Conditions: Protect from freezing. Discard unused reconstituted solution after the stated time.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs, cats, and horses. Not approved for food animals in the US, but may be used extra-label.

Extra-Label (Off-Label) Use: In the US, extra-label use in food animals is permitted under AMDUCA with a valid veterinary-client-patient relationship, but requires extended withdrawal times. Consult FARAD for specific withdrawal recommendations.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Cefazolin is a first-generation cephalosporin commonly used in veterinary medicine for surgical prophylaxis and treatment of susceptible bacterial infections. It is particularly effective against gram-positive cocci and some gram-negative organisms. Due to its short half-life, frequent dosing is required. It is generally well-tolerated, but caution is needed in animals with renal impairment. For surgical prophylaxis, it should be administered within 30-60 minutes before incision and repeated during prolonged procedures. In food animals, its use is limited by withdrawal times and availability of other approved drugs. Always perform culture and sensitivity testing when possible to ensure appropriate antibiotic selection.

References & Literature

  • πŸ“š Plumb's Veterinary Drug Handbook
  • πŸ“š Papich Veterinary Pharmacology and Therapeutics
  • πŸ“š Compendium of Veterinary Products (CVP)