What is the recommended dose of Cefazolin (Cefazolin) for treating infections, considering factors like infection severity and renal impairment (Impaired renal function)?

Cefazolin Dosing Recommendations

For adults with normal renal function treating serious infections, cefazolin should be dosed at 1-2 grams intravenously every 8 hours, with the higher end of this range (2 grams every 8 hours) preferred for severe infections. 1

Standard Adult Dosing (Normal Renal Function)

• The recommended dose is 1-2 grams IV every 8 hours for complicated intra-abdominal infections and other serious bacterial infections 1
• For severe infections requiring maximal bactericidal activity, use 2 grams every 8 hours rather than lower doses 1
• The FDA label confirms dosing intervals should be at least 8 hours for patients with creatinine clearance ≥55 mL/min or serum creatinine ≤1.5 mg/dL 2

Renal Dose Adjustments

Dose reduction is critical in renal impairment to prevent neurotoxicity and seizures. 2, 3, 4

Dosing Algorithm by Creatinine Clearance:

• CrCl ≥55 mL/min (SCr ≤1.5 mg/dL): Full dose of 1-2 grams every 8 hours 2

• CrCl 35-54 mL/min (SCr 1.6-3.0 mg/dL): Full dose but extend interval to every 12 hours minimum 2

• CrCl 11-34 mL/min (SCr 3.1-4.5 mg/dL): Give 50% of usual dose every 12 hours after loading dose 2

• CrCl ≤10 mL/min (SCr ≥4.6 mg/dL): Give 50% of usual dose every 18-24 hours after loading dose 2

• All reduced dosing requires an initial loading dose appropriate to infection severity 2

Pediatric Dosing

• For mild to moderate infections: 25-50 mg/kg/day divided into 3-4 equal doses 2
• For severe infections: Up to 100 mg/kg/day (maximum 45 mg/lb/day) divided into doses 2
• Not recommended for premature infants and neonates due to lack of safety data 2

Pediatric Renal Impairment:

• CrCl 40-70 mL/min: 60% of normal daily dose divided every 12 hours 2
• CrCl 20-40 mL/min: 25% of normal daily dose divided every 12 hours 2
• CrCl 5-20 mL/min: 10% of normal daily dose every 24 hours 2

High Body Weight Patients

• Patients >120 kg can safely receive up to 9 grams/day (3 grams every 8 hours) for bacteremia or skin/soft tissue infections 5
• This higher dosing showed no increase in treatment-emergent adverse events compared to standard dosing 5
• Consider weight-based dosing for optimal outcomes in patients with obesity 5

Critical Safety Considerations

Neurotoxicity Risk Factors:

Cefazolin can cause encephalopathy and seizures, particularly when dosed inappropriately in renal dysfunction. 3, 4

The following factors dramatically increase neurotoxicity risk:

• Renal impairment without dose adjustment 3, 4
• Advanced age (>80 years) 3
• Pre-existing CNS conditions (prior stroke, cognitive impairment, seizure history) 3
• Excessive dosing (e.g., 2 grams every 4 hours instead of every 8-12 hours) 3

Common Pitfall:

The most dangerous error is using standard 8-hour dosing intervals in patients with renal dysfunction. A case report documented fatal seizures in an 87-year-old receiving 2 grams every 4 hours with renal impairment, when appropriate dosing would have been 2 grams every 12 hours 3. Another case showed seizures in a hemodialysis patient receiving 2 grams every 8 hours for 25 days 4.

Administration Guidelines

• IV bolus injection: Dilute reconstituted vial with approximately 5 mL sterile water and inject slowly over 3-5 minutes 2
• Intermittent infusion: Dilute in 50-100 mL compatible solution 2
• Reconstituted solutions stable for 24 hours at room temperature or 10 days refrigerated 2

Surgical Prophylaxis Context

While not the primary question, note that surgical prophylaxis uses different timing: 0.5-1 hour preoperatively, with possible continuation for 3-5 days post-operatively for high-risk procedures (open-heart surgery, prosthetic arthroplasty) 2.