1st Generation Cephalosporin (Surgical Antibiotic Prophylaxis) Pregnancy: Animal studies do not indicate reproductive toxicity, but cefazolin crosses the placenta and experience is insufficient - use in pregnancy, especially the first trimester, only after careful benefit-risk assessment and preferably avoided unless absolutely necessary. Excreted in breast milk at very low concentrations; use during breast-feeding only after careful benefit/risk assessment.

Cefazolin (Surgical Prophylaxis)

Brand names: Kefzol

Cefazolin is a first-generation cephalosporin antibiotic widely used intravenously for surgical antibiotic prophylaxis across many procedures.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 1 g cefazolin

Route: Intravenous - by slow intravenous injection or by intravenous infusion after dilution. Single doses exceeding 1 g should be given as intravenous infusion. Not for intrathecal administration. If lidocaine is used as a solvent the resulting solution must never be given intravenously.

Frequency: Single dose 30-60 minutes before surgery. For long surgical procedures (2 hours or more), an additional 0.5 to 1 g cefazolin during the intervention.

Max: No maximum is stated for perioperative prophylaxis. For treatment of infection the SPC states that in severe infections doses up to 6 g per day can be administered in three or four equal doses (one dose every 6 to 8 hours).

Perioperative prophylaxis regimen taken verbatim from the SPC 'Special dosage recommendations - Perioperative prophylaxis': 1 g cefazolin 30-60 minutes before surgery to prevent postoperative infection in contaminated or potentially contaminated surgery; additional 0.5 to 1 g during procedures of 2 hours or more; prolonged continuation of administration beyond the surgical intervention should be supported by national official guidance. The SPC stresses that (1) the preoperative dose is given just (30 minutes to 1 hour) prior to the start of surgery so adequate antibiotic levels are present in serum and tissues at initial surgical incision, and (2) cefazolin be administered, if necessary, at appropriate intervals during surgery. TREATMENT (non-prophylaxis) doses stated in the same SPC for adults and adolescents over 12 years and at least 40 kg: sensitive microorganisms 1 g to 2 g per day divided into 2-3 equal doses; moderately sensitive microorganisms 3 g to 4 g per day divided into 3-4 equal doses; severe infections up to 6 g per day in three or four equal doses. Elderly: no dose adjustment required with normal renal function. Duration of treatment depends on severity of infection and clinical/bacteriological progress. NOTE: the fetched SPC sections 4.4 and 4.8 were truncated at the source-fetch limit, so the retrieved text is not necessarily the complete SPC content. Source quote: 'Perioperative prophylaxis - To prevent postoperative infection in contaminated or potentially contaminated surgery, the recommended doses are: 1 g cefazolin 30-60 minutes before surgery. In case of long surgical procedures (2 hours or more), additional 0.5 to 1 g cefazolin during the intervention.' (Cefazolin 2g Powder for solution for infusion/injection vials SPC, section 4.2).

Paediatric dose

Route: Intravenous injection or intravenous infusion

Frequency: Total daily dose divided into 2 to 4 equal doses per day (one dose every 6, 8 or 12 hours)

Max: Up to 100 mg/kg bodyweight per day for moderately sensitive microorganisms, divided into 3 or 4 equal doses (one dose every 6 or 8 hours)

SPC states 25-50 mg/kg bodyweight per day for infections caused by sensitive microorganisms, divided into 2 to 4 equal doses; and up to 100 mg/kg bodyweight per day for moderately sensitive microorganisms, divided into 3 or 4 equal doses. A single dosePerKg number is NOT given - the SPC states a range, so dosePerKg is left null deliberately. IMPORTANT: this is the SPC paediatric dose for TREATMENT OF INFECTION; the SPC gives no separate paediatric perioperative prophylaxis dose. Use of cefazolin is not recommended in premature babies and infants less than 1 month of age (safety not established). Paediatric renal impairment: moderate impairment (creatinine clearance 40-20 ml/min) 25% of the normal daily dose divided into doses every 12 hours; severe impairment (creatinine 20-5 mL/min) 10% of normal daily dose given every 24 hours - valid after an initial starting dose. Verify all paediatric dosing against a children's formulary before use.

Dose adjustments

Renal

Adults - dose guided by blood levels where possible, otherwise by creatinine clearance: CrCl 55 ml/min or more (serum creatinine 1.5 mg/100 ml or less) normal dose and normal dosing interval; CrCl 35-54 (creatinine 1.6-3.0) normal dose every 8 hours; CrCl 11-34 (creatinine 3.1-4.5) half the normal dose every 12 hours; CrCl 10 ml/min or less (creatinine 4.6 or more) half the normal dose every 18-24 hours. In haemodialysis patients the schedule depends on dialysis conditions. Monitor renal function especially in severely ill patients on maximum doses and with concomitant nephrotoxic agents.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance
History of severe hypersensitivity (e.g. anaphylactic reaction) to other beta-lactam antibiotics (penicillins, monobactams and carbapenems)
Contraindications to lidocaine must be excluded before intramuscular injection of cefazolin when lidocaine solution is used as a solvent; cefazolin solutions containing lidocaine must never be administered intravenously

Side effects

Gastrointestinal: nausea, vomiting, diarrhoea; pseudomembranous colitis (stop cefazolin immediately; antiperistaltic agents are contraindicated)
Hypersensitivity: rash, erythema, urticaria, angioedema; anaphylactic shock; Stevens-Johnson syndrome and toxic epidermal necrolysis (rare/very rare)
Infections: oral and genital candidiasis; overgrowth of non-susceptible organisms with prolonged use
Blood: leukopenia, granulocytopenia, neutropenia, thrombocytopenia, eosinophilia (rare and reversible); coagulation disorders with subsequent bleeding
Hepatobiliary: transient elevation of AST, ALT, alkaline phosphatase, gamma-GT, bilirubin and/or LDH; transient hepatitis and transient cholestatic jaundice
Renal: nephrotoxicity, interstitial nephritis, proteinuria, transient elevation of blood urea nitrogen (usually with concomitant nephrotoxic agents); seizures reported in renal dysfunction treated with inappropriately high doses
Cardiac: Kounis syndrome (allergic/hypersensitivity-associated coronary vasospasm)

Interactions

Probenecid - may decrease renal tubular secretion of cephalosporins when used concurrently, resulting in increased and more prolonged cephalosporin blood levels (US FDA label; UK SPC section 4.5 was not in the fetched bundle)
Laboratory interference - false positive urine glucose with Benedict's solution, Fehling's solution or CLINITEST tablets (not with enzyme-based tests); positive direct and indirect antiglobulin (Coombs) tests have occurred (US FDA label)

Clinical monograph

How it works

It inhibits bacterial cell wall synthesis by binding penicillin-binding proteins, providing reliable activity against staphylococci and streptococci.

Prescribing in practice

Give the prophylactic dose within the recommended window before surgical incision to ensure adequate tissue concentrations at the time of incision.
Avoid or use with caution in patients with a history of severe penicillin or cephalosporin allergy and check local microbiology policy.
Redosing during prolonged procedures or major blood loss may be required per local protocol.

Monitoring

Monitor for hypersensitivity reactions and, with prolonged use, renal function and signs of antibiotic-associated diarrhoea.

Counselling the patient

Tell the team about any previous reactions to penicillins or cephalosporins before surgery.
Report rash, breathlessness or swelling promptly as these may indicate allergy.
Report severe or persistent diarrhoea after antibiotic use.

Evidence & guidelines

Cefazolin is recommended for surgical prophylaxis in many procedures by national guidance including NICE and SIGN.

Reference: WHO SSI Guidelines 2016; SIGN 104 Antibiotic Prophylaxis in Surgery; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways