cefazolin
first-generation cephalosporin· Brands: Ancef, Kefzol, Cefamezin, Zolicef, CefacidalIMIV
Mechanism of action
Cefazolin is a first-generation cephalosporin antibiotic. It inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death. It has bactericidal activity against susceptible gram-positive organisms, including staphylococci and streptococci, but is less active against gram-negative bacteria.
Pharmacokinetics
Cefazolin is administered parenterally, typically intravenously or intramuscularly. It is well absorbed after IM injection, with peak serum concentrations achieved within 1 to 2 hours. It is widely distributed in body fluids and tissues, including bone and synovial fluid. It is not significantly metabolized; approximately 80-90% is excreted unchanged in the urine via glomerular filtration and tubular secretion. The half-life is about 1.5 to 2 hours in patients with normal renal function and is prolonged in renal impairment.
Indications & dosing
Surgical prophylaxis
Administer within 60 min before incision; repeat for prolonged procedures.
- adult · IV: 2 g pre-op single · Administer within 60 min before incision; repeat for prolonged procedures.
Skin and soft tissue infections
Adjust dose in renal impairment; duration depends on clinical response.
- adult · IV: 1–2 g every 8 hours · Adjust dose in renal impairment; duration depends on clinical response.
Bone and joint infections
Consider adding rifampicin for prosthetic joint infections.
- adult · IV: 1–2 g every 8 hours · Consider adding rifampicin for prosthetic joint infections.
Contraindications & precautions
- Hypersensitivity to cefazolin or other cephalosporins · Do not use in patients with a history of immediate or severe reaction to cephalosporins.
- Hypersensitivity to penicillins · Cross-reactivity may occur; use with caution, especially if the penicillin reaction was anaphylactic.
- Use with caution in renal impairment; reduce dose as necessary.
- Use with caution in patients with penicillin hypersensitivity, especially those with a history of anaphylaxis.
- Monitor for signs of superinfection, particularly with prolonged use.
- Use with caution in patients with a history of gastrointestinal disease, especially colitis.
- Ensure adequate time between administration and surgical incision for prophylaxis.
Adverse effects
- Pain and inflammation at injection site
- Diarrhoea
- Nausea
- Skin rash
- Anaphylaxisserious
- Clostridioides difficile-associated diarrhoeaserious
- Seizuresserious
- Blood dyscrasias (e.g., neutropenia, thrombocytopenia)serious
Renal & hepatic adjustment
- eGFR 30–300: No adjustment required; use usual dosing.
- eGFR 10–29: Administer the usual dose every 12 hours instead of every 8 hours.
- eGFR 0–9: Administer the usual dose every 24 hours instead of every 8 hours.
Monitoring, pregnancy & toxicity
- Renal function (serum creatinine, eGFR) · Before treatment and periodically during therapy, especially in patients with renal impairment or receiving nephrotoxic drugs.
- Complete blood count (CBC) with differential · Baseline and periodically during prolonged therapy.
- Signs of superinfection (e.g., oral or vaginal candidiasis) · Throughout treatment.
- Prothrombin time/INR · In patients at risk of bleeding or on anticoagulants.
- Pregnancy: Cefazolin is generally considered safe in pregnancy. It is used for surgical prophylaxis and treatment of infections. It crosses the placenta but has not been associated with fetal harm when used as indicated.
- Toxicity: Allergic reactions, ranging from rash to anaphylaxis · Discontinue cefazolin. For anaphylaxis, administer epinephrine, oxygen, IV fluids, and antihistamines/corticosteroids as needed. Consider an alternative class of antibiotics.
- Toxicity: Gastrointestinal effects, including diarrhoea, nausea, and Clostridioides difficile-associated colitis · Assess severity. If C. difficile infection is suspected, discontinue cefazolin and initiate appropriate therapy (e.g., oral vancomycin or fidaxomicin) with supportive care.
- Toxicity: Nephrotoxicity, particularly in patients with pre-existing renal impairment or concurrent nephrotoxin use · Monitor renal function, adjust dose based on renal function, and consider alternative therapy if renal injury occurs.
- Toxicity: Neurotoxicity, including agitation, myoclonus, or seizures, especially with high doses in renal impairment · Discontinue the drug, reduce dose in renal impairment, and manage seizures with anticonvulsants if necessary.
Clinical notes
Cefazolin is commonly used for surgical prophylaxis, particularly in cardiac, orthopedic, and abdominal surgeries. It is effective against methicillin-sensitive Staphylococcus aureus and some gram-negative organisms. It is not effective against methicillin-resistant S. aureus (MRSA) or enterococci. It is the drug of choice for surgical prophylaxis because of its good spectrum, safety, and long half-life. Doses must be adjusted in renal impairment. It can cause allergic reactions in patients with penicillin hypersensitivity due to cross-reactivity. It is available as a powder for reconstitution.
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BNF; local formulary