Cefazolin !

A first-generation intravenous cephalosporin: the usual choice for antibiotic prophylaxis in surgery and for serious infections by susceptible S. aureus.

Updated 2026-11-01

Class: Beta-lactams
Enzyme: Penicillin-binding proteins (bacterial transpeptidases)
ATC code: J01DB04
WHO Model List of Essential Medicines

Penicillin-binding proteins (bacterial transpeptidases)Cefazolin

The figure shows cephalothin, a first-generation cephalosporin with the same core, acylating the Streptomyces R61 DD-peptidase, the classic PBP model; no structure of this drug bound to a PBP has been published.

Target in 3D: Penicillin-binding proteins (bacterial transpeptidases). PDB structure 1CEG (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Cefazolin acylates the PBPs and blocks peptidoglycan cross-linking. Like other first-generation agents, it is very active against methicillin-susceptible Staphylococcus aureus and streptococci, and against some E. coli, Klebsiella and Proteus mirabilis. It reaches most tissues well but not the central nervous system, so it is not used for meningitis.

Given before the incision and reaches the tissues
Acylates the PBPs of staphylococci and streptococci
Bacteria contaminating the wound cannot build their wall
They lyse before an infection is established

Pharmacokinetics

Absorption: Intravenous or intramuscular.
Distribution: Good penetration into soft tissue and bone; it does not reach the meninges.
Elimination: By the kidney, unchanged; adjusted in kidney failure.
Half-life: About 1.8 hours intravenously.

Indications

Perioperative prophylaxis in many clean and clean-contaminated operations.
Bacteraemia and endocarditis due to methicillin-susceptible S. aureus. Infective endocarditis →
Skin and soft-tissue infections. Cellulitis of the leg →
Bone and joint infections. Osteomyelitis →
Urinary tract infections by susceptible strains. Urinary tract infection (acute cystitis) →

Adverse effects

Common

Injection-site pain and phlebitis
Diarrhoea, nausea
Rash, eosinophilia, transient transaminase rise

Contraindications

Known allergy to cephalosporins

Key interactions

Oral anticoagulants (warfarin): Cephalosporins can lower prothrombin activity; the INR is monitored.
Probenecid: Reduces tubular secretion: higher and longer-lasting β-lactam levels.

What is monitored

Kidney function
Prothrombin time in patients at risk (malnutrition, long courses, anticoagulants)
Blood count in long courses

Administration and safety

Intravenous (slow injection or infusion) or intramuscular.
In surgical prophylaxis, timing matters: it is given before the incision according to the unit's protocol and repeated in long operations when the protocol says so.
Do not confuse cefazolin with cefalexin, cefoxitin or ceftriaxone.

Nursing care

Before the first dose: ask about allergy to penicillins, cephalosporins and other β-lactams, and what the reaction was.
After the first dose, watch for hives, wheeze, low blood pressure or swelling of lips and tongue, with anaphylaxis equipment at hand.
In theatre, record the time of administration relative to the incision.
Check the IV site for phlebitis.
Teach the patient to report watery or bloody diarrhoea, even weeks after the course ends.

Pregnancy and breastfeeding

Animal studies showed no fetal harm and there are no controlled studies in pregnant women; used if clearly needed.

Test yourself

Think of the answer, then tap the question to see it.

Why is cefazolin the usual prophylaxis for clean surgery?

Because it covers skin gram-positive cocci (susceptible S. aureus and streptococci), penetrates tissues well, is well tolerated and is cheap.

Can cefazolin treat meningitis due to susceptible S. aureus?

No: it does not penetrate the central nervous system.

Which patients are at risk of low prothrombin with cephalosporins such as cefazolin?

Those with kidney or liver failure, malnutrition, long courses or anticoagulants; prothrombin time is monitored and vitamin K given if needed.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Cefazolin Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - CEFAZOLIN injection, powder, for solution (DailyMed (U.S. National Library of Medicine), 2026); RCSB PDB - 1CEG: CEPHALOTHIN COMPLEXED WITH DD-PEPTIDASE (RCSB Protein Data Bank, 2026); Farmacología básica y clínica (Katzung), cap. 43 (McGraw Hill, 2025).

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Representative model, for educational purposes only.