What is the recommended dose of intravenous (IV) cefazolin?

IV Cefazolin Dosing

For most adult infections, cefazolin is dosed at 1-2 grams IV every 8 hours, with surgical prophylaxis typically requiring 2 grams as a single preoperative dose. 1

Standard Adult Dosing by Infection Severity

Mild infections caused by susceptible gram-positive cocci:

• 250-500 mg IV every 8 hours 1

Moderate to severe infections:

• 500 mg to 1 gram IV every 6-8 hours 1
• For urologic procedures: 1 gram IV every 8 hours 2

Severe, life-threatening infections (endocarditis, septicemia):

• 1-1.5 grams IV every 6 hours 1
• In rare instances, doses up to 12 grams per day have been used 1

Acute uncomplicated urinary tract infections:

• 1 gram IV every 12 hours 1

Pneumococcal pneumonia:

• 500 mg IV every 12 hours 1

Surgical Prophylaxis Dosing

Standard surgical prophylaxis:

• 2 grams IV administered 30-60 minutes prior to incision 2
• Redose with 1 gram if procedure duration exceeds 4 hours 2
• Postoperatively: 500 mg to 1 gram IV every 6-8 hours for 24 hours 1

Cardiac surgery:

• 2 grams IV plus 1 gram in cardiopulmonary bypass priming solution 2
• Redose 1 gram at the 4th hour intraoperatively 2

Neurosurgery and spine surgery with implants:

• 2 grams IV slow as single dose 2
• Redose 1 gram if duration exceeds 4 hours 2

Pediatric Dosing

Mild to moderately severe infections:

• 25-50 mg/kg/day divided into 3-4 equal doses 1

Severe infections:

• Up to 100 mg/kg/day (maximum 45 mg/lb/day) 1

Staphylococcal infections (including MSSA):

• 150 mg/kg/day divided every 8 hours 3

Infective endocarditis:

• 100 mg/kg/day IV divided every 8 hours (maximum 12 grams daily) 3, 4

CNS infections:

• 100 mg/kg/day divided every 8 hours to ensure adequate CNS penetration 3

Important note: Safety has not been established in premature infants and neonates; use is not recommended in these populations 1

Renal Dose Adjustments

Critical caveat: Failure to adjust cefazolin dosing in renal impairment can lead to drug accumulation, neurotoxicity, and seizures, particularly in elderly patients with pre-existing CNS conditions 5, 6. This is a common and potentially fatal pitfall.

Creatinine clearance ≥55 mL/min or serum creatinine ≤1.5 mg/dL:

• Full doses without adjustment 1

Creatinine clearance 35-54 mL/min or serum creatinine 1.6-3.0 mg/dL:

• Full doses but extend interval to at least every 8 hours 1

Creatinine clearance 11-34 mL/min or serum creatinine 3.1-4.5 mg/dL:

• Half the usual dose every 12 hours (after loading dose) 1

Creatinine clearance ≤10 mL/min or serum creatinine ≥4.6 mg/dL:

• Half the usual dose every 18-24 hours (after loading dose) 1

Pediatric renal impairment:

• CrCl 70-40 mL/min: 60% of normal daily dose divided every 12 hours 1
• CrCl 40-20 mL/min: 25% of normal daily dose divided every 12 hours 1
• CrCl 20-5 mL/min: 10% of normal daily dose every 24 hours 1

All reduced dosage recommendations apply after an appropriate initial loading dose based on infection severity 1.

Administration Considerations

Direct IV bolus injection:

• Reconstitute and further dilute with approximately 5 mL Sterile Water for Injection 1
• Inject slowly over 3-5 minutes 1

Intermittent or continuous infusion:

• Dilute reconstituted solution in 50-100 mL of compatible IV fluid 1

Stability:

• Reconstituted solutions stable for 24 hours at room temperature or 10 days refrigerated 1

Key Clinical Pearls

The serum half-life of cefazolin averages 1.75-2.22 hours in patients with normal renal function 7, but can be significantly prolonged in elderly patients even without obvious renal impairment 8. A linear correlation exists between elimination rate and creatinine clearance (Ke = 0.022 + 0.0028 × CrCl) 7, making dose adjustment calculations straightforward.

Tissue penetration is generally excellent, with tissue-to-serum free drug AUC ratios approximating 1.06 in lower limb infections 9, suggesting adequate tissue exposure for most soft tissue infections when dosed appropriately.