Clinical safety rating: safe
Human studies have proved safety
Cefazolin is a first-generation cephalosporin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), thereby inhibiting transpeptidation and disrupting peptidoglycan cross-linking. This leads to cell lysis and death primarily in susceptible gram-positive bacteria.
| Metabolism | Cefazolin undergoes minimal hepatic metabolism; it is primarily excreted unchanged in the urine via glomerular filtration and tubular secretion. The drug is not significantly metabolized by the liver. |
| Excretion | Renal: 80–90% unchanged via glomerular filtration and tubular secretion; biliary: <1%; fecal: negligible. |
| Half-life | 1.8 hours in normal renal function; extends to 30–70 hours in end-stage renal disease (CrCl <10 mL/min). |
| Protein binding | 80% bound to albumin. |
| Volume of Distribution | 0.12–0.14 L/kg; approximates extracellular fluid volume, indicating low tissue penetration. |
| Bioavailability | Intramuscular: 100% (complete absorption). |
| Onset of Action | Intravenous: immediate; intramuscular: 15–30 minutes. |
| Duration of Action | 6–8 hours in normal renal function; prolonged in renal impairment. |
| Molecular Weight | 454.51 |
1-2 g IV/IM every 6-8 hours; maximum 12 g/day.
| Renal impairment | CrCl >55 mL/min: no adjustment; CrCl 35-54 mL/min: 1-2 g every 8 hours; CrCl 11-34 mL/min: 500 mg-1 g every 12 hours; CrCl ≤10 mL/min: 500 mg-1 g every 24-48 hours. |
| Liver impairment | No dosage adjustment required for hepatic impairment. |
| Pediatric use | 50-100 mg/kg/day IV/IM divided every 8 hours; severe infections: 100 mg/kg/day divided every 6-8 hours. |
| Geriatric use | No specific adjustment based solely on age; dose adjustment based on renal function per CrCl. |
| 1st trimester | Cefazolin is generally considered safe in the first trimester. Studies have not shown an increased risk of major birth defects. It should be used only if clearly needed. |
| 2nd trimester | Safe for use in the second trimester. No known adverse fetal effects. Risk-benefit assessment recommends use when indicated. |
| 3rd trimester | Safe for use in the third trimester. No known adverse fetal effects. Prophylactic use in cesarean delivery is common. |
Clinical note
Safe IV cephalosporin used for surgical prophylaxis (cesarean section), GBS prophylaxis in penicillin-allergic women at low anaphylaxis risk, and treatment of skin/soft tissue infections. No evidence of teratogenicity. Standard agent for cesarean section prophylaxis per ACOG.
| Placental transfer | Cefazolin crosses the placenta readily. Therapeutic concentrations are achieved in fetal serum and tissues. Evidence: Extensive. |
| Breastfeeding |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to cefazolin or cephalosporinsSevere hypersensitivity to penicillins (immediate type)
| Precautions | Hypersensitivity reactions (including anaphylaxis) may occur; cross-allergenicity among cephalosporins and penicillins is possible., Clostridioides difficile-associated diarrhea (CDAD) can occur with antibiotic use., Dosage adjustment required in patients with renal impairment due to predominantly renal elimination., Prolonged use may result in overgrowth of nonsusceptible organisms (e.g., Candida, Pseudomonas)., Seizures may occur with high doses, especially in patients with renal impairment. |
| Food/Dietary | No significant food interactions. Alcohol should be avoided during treatment and for at least 72 hours after last dose due to potential disulfiram-like reaction (nausea, vomiting, flushing). |
Loading safety data…
| Cefazolin is excreted into breast milk in low concentrations. The amount is unlikely to cause adverse effects in breastfed infants. Compatible with breastfeeding; minimal risk. |
| Lactation Rating | L1 (Safe) |
| Teratogenic Risk | Cefazolin is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and adequate, well-controlled studies in pregnant women are lacking. Generally considered safe throughout pregnancy; no known teratogenic effects in the first trimester. Use only if clearly needed. |
| Fetal Monitoring | Monitor maternal renal function (serum creatinine, BUN) and liver function tests periodically. In prolonged therapy, monitor for superinfection or bleeding diathesis due to hypoprothrombinemia. No specific fetal monitoring required beyond routine obstetric care. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies have not shown impaired fertility. |
| Clinical Pearls | Cefazolin is a first-generation cephalosporin with a short half-life; requires dose adjustment in renal impairment. Watch for cross-allergenicity in penicillin-allergic patients (approx. 10% risk). Administer parenterally only; no oral formulation available. Common surgical prophylaxis antibiotic due to good coverage of skin flora. |
| Patient Advice | This medication is given by injection or IV, not by mouth. · Report any signs of allergic reaction: rash, hives, itching, difficulty breathing. · May cause diarrhea; notify your doctor if severe or persistent. · Avoid alcohol while taking this medication to prevent disulfiram-like reaction. · Complete the full course as prescribed even if you feel better. |