What is the dosage and administration of Cefazolin (a cephalosporin antibiotic) for treating bacterial infections?

Cefazolin Dosage and Administration for Bacterial Infections

The recommended dosage of cefazolin for treating moderate to severe bacterial infections in adults is 500 mg to 1 gram administered intravenously or intramuscularly every 6 to 8 hours, with dosage adjustments based on infection severity, site, and renal function. 1

Standard Adult Dosing Regimens

• For moderate to severe infections: 500 mg to 1 gram every 6 to 8 hours 1
• For mild infections caused by susceptible gram-positive cocci: 250 mg to 500 mg every 8 hours 1
• For acute, uncomplicated urinary tract infections: 1 gram every 12 hours 1
• For pneumococcal pneumonia: 500 mg every 12 hours 1
• For severe, life-threatening infections (e.g., endocarditis, septicemia): 1 gram to 1.5 grams every 6 hours 1
• In rare instances, doses up to 12 grams per day have been used for severe infections 1

Specific Infection Types

Skin and Soft Tissue Infections

• For Staphylococcus aureus infections: Cefazolin 1 gram every 8 hours IV 2
• For surgical site infections: Cefazolin is effective for methicillin-susceptible S. aureus (MSSA) infections 2

Perioperative Prophylaxis

• 1 gram IV administered 30 minutes to 1 hour prior to surgery 1
• For lengthy procedures (≥2 hours): Additional 500 mg to 1 gram IV during surgery 1
• Postoperatively: 500 mg to 1 gram IV every 6 to 8 hours for 24 hours 1
• For high-risk surgeries (e.g., open-heart surgery, prosthetic arthroplasty): May continue for 3 to 5 days postoperatively 1

Dosage Adjustment for Renal Impairment

• Creatinine clearance ≥55 mL/min or serum creatinine ≤1.5 mg%: Full dose at normal intervals 1
• Creatinine clearance 35-54 mL/min or serum creatinine 1.6-3.0 mg%: Full dose at minimum 8-hour intervals 1
• Creatinine clearance 11-34 mL/min or serum creatinine 3.1-4.5 mg%: Half the usual dose every 12 hours 1
• Creatinine clearance ≤10 mL/min or serum creatinine ≥4.6 mg%: Half the usual dose every 18-24 hours 1

Pediatric Dosing

• Total daily dosage: 25-50 mg/kg divided into 3 or 4 equal doses for most mild to moderately severe infections 1
• For severe infections: May increase to 100 mg/kg/day 1
• Not recommended for premature infants and neonates due to lack of safety data 1
• For pediatric patients with renal impairment:
  • Moderate impairment (CrCl 70-40 mL/min): 60% of normal daily dose every 12 hours 1
  • Moderate to severe impairment (CrCl 40-20 mL/min): 25% of normal daily dose every 12 hours 1
  • Severe impairment (CrCl 20-5 mL/min): 10% of normal daily dose every 24 hours 1

Administration Methods

Intramuscular Administration

• Reconstitute with Sterile Water for Injection 1
• For 500 mg vial: Add 2 mL diluent (yields approximately 225 mg/mL) 1
• For 1 g vial: Add 2.5 mL diluent (yields approximately 330 mg/mL) 1
• Inject into a large muscle mass 1

Intravenous Administration

• Direct (bolus) injection: Further dilute reconstituted solution with approximately 5 mL Sterile Water for Injection and inject slowly over 3-5 minutes 1
• Intermittent or continuous infusion: Dilute in 50-100 mL of compatible solution (e.g., Sodium Chloride Injection, 5% Dextrose Injection) 1

Clinical Considerations

• Cefazolin has strong activity against gram-positive bacteria, particularly Staphylococcus aureus, and many gram-negative organisms except Pseudomonas aeruginosa 3, 4
• Continuous infusion may provide pharmacokinetic and pharmacodynamic advantages over intermittent administration, including more stable serum levels, lower interpatient variability, and higher tissue penetration 5
• For mixed infections involving anaerobes, additional coverage may be needed as cefazolin has limited anaerobic activity 2
• For surgical prophylaxis, timing is critical - administer 30-60 minutes before incision to ensure adequate tissue levels at the time of initial surgical incision 1

Common Pitfalls to Avoid

• Failing to adjust dosage in patients with renal impairment, which can lead to drug accumulation and toxicity 1
• Inadequate dosing in severe infections, which may result in treatment failure 1
• Inappropriate timing of preoperative prophylactic dose, reducing effectiveness of surgical prophylaxis 1
• Not considering local resistance patterns when selecting cefazolin for empiric therapy 6
• Using cefazolin alone for mixed infections involving anaerobes or Pseudomonas aeruginosa, which are not adequately covered 3, 4