Cefazolin
Cefazolin sodium
Brand names:Ancef, Kefzol
A first-generation parenteral cephalosporin and the most administered antibiotic in American hospitals due to its dominant role in surgical antimicrobial prophylaxis. In tactical EMS, cefazolin is the IV gram-positive workhorse for prolonged field care, role 2 surgical settings, and as the parenteral alternative when oral cefadroxil is not feasible.
Pharmacology and Actions
Cefazolin is a first-generation cephalosporin that binds penicillin-binding proteins (PBPs), inhibiting peptidoglycan cross-linking in bacterial cell wall synthesis. Bactericidal. Spectrum: excellent gram-positive coverage including methicillin-susceptible Staphylococcus aureus and streptococci; modest gram-negative coverage (E. coli, Klebsiella, Proteus mirabilis). No coverage for MRSA, enterococci, atypicals, or Pseudomonas.
Indications
- Surgical antimicrobial prophylaxis (most common indication)
- Skin and soft tissue infection (cellulitis, abscess, surgical wound infection)
- Methicillin-susceptible Staphylococcus aureus bacteremia and endocarditis
- Bone and joint infection (MSSA)
- Urinary tract infection (gram-positive coverage)
- Wound infection prophylaxis in penetrating extremity trauma when oral antibiotics not feasible
Absolute Contraindications
- Known hypersensitivity to cefazolin or other cephalosporins
- Anaphylaxis or severe immediate hypersensitivity reaction to any beta-lactam (penicillin, cephalosporin, carbapenem)
Precautions and Side Effects
Common: GI - diarrhea, nausea, C. difficile colitis. Hypersensitivity: rash 1 to 3 percent, urticaria, rare anaphylaxis. Hematologic: eosinophilia, rare thrombocytopenia and neutropenia with prolonged use. Injection site reactions. Seizures at very high doses or in renal impairment. Drug interactions: probenecid increases cefazolin levels (occasionally used therapeutically); concurrent aminoglycosides may increase nephrotoxicity; no significant CYP450 interactions. Half-life 1.5 to 2 hours, prolonged in renal impairment - dose adjust if CrCl under 55. Pregnancy Category B (extensive use in pregnancy including for surgical prophylaxis). Compatible with lactation (small amounts in breast milk). Standard pediatric dosing. Mild or remote penicillin allergy without anaphylaxis is not a true contraindication - first-generation cephalosporin cross-reactivity is approximately 1 to 2 percent in true penicillin allergy and far lower for non-anaphylactic reactions.
Adult Dosing
Pediatric Dosing
25 to 100 mg/kg/day IV/IM divided every 6 to 8 hours. Surgical prophylaxis: 30 mg/kg IV within 60 minutes before incision.
Pharmacokinetics
Peak Effect: 30 minutes to 1 hour.
Duration: 6 to 8 hours.
Storage and Handling
Powder for reconstitution: room temperature, protect from light. Reconstituted solution: stable 24 hours at room temperature, 96 hours refrigerated. Premixed bags: per labeling.
Reconstitution:
Reconstitute 1 g vial with 2.5 mL sterile water or 0.9 percent saline for IM use (yields 330 mg/mL after displacement). For IV bolus: dilute reconstituted solution further to at least 10 mL in compatible fluid and infuse over 3 to 5 minutes. For IV infusion: dilute in 50 to 100 mL of NS, D5W, or LR and infuse over 15 to 30 minutes.
TCCC and TECC Role
Cefazolin is not in the TCCC core formulary for wound prophylaxis (TCCC 2026 uses cefadroxil PO or ceftriaxone IV/IM). Cefazolin's tactical role is in higher levels of care: prolonged field care, role 2 surgical settings, MASCAL surgical prophylaxis, or as a parenteral gram-positive antibiotic when oral cefadroxil is not feasible and ceftriaxone is unavailable. In TEMS supplemental formularies, it appears as the IV gram-positive workhorse for surgical and skin infection management.
Cefazolin is the surgical prophylaxis antibiotic - the most administered antibiotic in American hospitals by some counts. Its tactical relevance grows in prolonged field care: if a casualty is held for more than the TCCC oral antibiotic window and is hemodynamically stable enough to consider operative debridement in role 2 settings, cefazolin becomes the parenteral gram-positive choice. For most tactical scenarios shorter than 12 hours from injury to definitive care, cefazolin is unnecessary - cefadroxil PO or ceftriaxone IV/IM remain the TCCC doctrine.
Withholding cefazolin from a patient with a remote, mild, or non-anaphylactic penicillin allergy. Modern cross-reactivity data suggest first-generation cephalosporins have only about 1 to 2 percent cross-reactivity with true penicillin allergy, and far less with non-anaphylactic reactions. Reflexively denying cefazolin to anyone who lists penicillin allergy leads to use of broader-spectrum, less effective alternatives. The other mistake is administering surgical prophylaxis too early (more than 60 minutes before incision) or too late (after incision) - timing matters and the evidence is clear.
This drug profile is provided as educational reference material for trained medical providers. It is not medical advice, not a substitute for formal training, and not a substitute for current published guidelines or medical direction.
Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances are subject to additional handling, accountability, and documentation requirements per DEA and state law. Always verify dosing, indications, contraindications, and route of administration against current published guidelines and your local protocols before administration.
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Drug information evolves. Last reviewed dates and source citations are provided for each entry. Confirm currency against the cited source before clinical use.
Penn Tactical Solutions publishes this reference for educational purposes. PTS does not provide medical direction and does not assume responsibility for clinical decisions made in the field. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Educational reference for trained medical providers. Not medical advice. Not a substitute for formal training, current published guidelines, or medical direction. Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances require additional storage, accountability, and documentation per DEA and state law.
In a medical emergency, call 911. This reference is not a substitute for emergency medical services.
Verify dosing, indications, and contraindications against current published guidelines and your local protocols before administration. Confirm content currency against the source citation. Penn Tactical Solutions does not provide medical direction. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Cefazolin
| IV/IO | 1 to 2 g IV every 8 hours for most indications. For surgical prophylaxis: 2 g IV within 60 minutes before incision; redose at 4 hours if procedure continues. For obese patients (over 120 kg): 3 g IV. Severe infection or MSSA bacteremia: 2 g IV every 8 hours. (Plasma levels within 15 minutes) |
| IM | 1 g IM every 8 hours. Reconstitute with 2.5 mL sterile water or 0.9 percent saline. IM administration is painful; use only when IV not available. (15 to 30 minutes) |
| IN | None (None) |
| PO | None (not available orally; cephalexin is the oral analog for outpatient gram-positive coverage). (None) |