What is the mechanism of action, safe administration guidelines, and nursing considerations for cefazolin (a first-generation cephalosporin antibiotic)?

Mechanism of Action, Safe Administration, and Nursing Considerations for Cefazolin

Cefazolin is a first-generation cephalosporin antibiotic that works by inhibiting bacterial cell wall synthesis and should be administered intravenously over 3-5 minutes for direct injection or 15-30 minutes for intermittent infusion, with careful monitoring for hypersensitivity reactions and renal function.

Mechanism of Action

Cefazolin is a first-generation cephalosporin antibiotic that works by:

• Binding to penicillin-binding proteins (PBPs) in bacterial cell walls
• Inhibiting the final transpeptidation step of peptidoglycan synthesis
• Preventing proper cell wall formation, leading to bacterial cell lysis and death
• Demonstrating bactericidal activity against primarily gram-positive organisms and some gram-negative bacteria 1, 2

Cefazolin is particularly effective against:

• Staphylococcus aureus (including penicillinase-producing strains but not MRSA)
• Streptococci
• Some Enterobacteriaceae (E. coli, Klebsiella, Proteus mirabilis)
• Not effective against Pseudomonas, Enterococcus, or MRSA 2

Safe Administration Guidelines

Dosage and Administration

For adults:

• Moderate to severe infections: 500 mg to 1 gram IV every 6-8 hours
• Mild infections: 250-500 mg IV every 8 hours
• Severe, life-threatening infections: 1-1.5 grams IV every 6 hours
• Surgical prophylaxis: 1 gram IV 30-60 minutes before incision 1

For pediatric patients:

• 25-50 mg/kg/day divided into 3-4 doses
• Up to 100 mg/kg/day for severe infections
• Not recommended for premature infants or neonates 1

Administration Methods

Intravenous administration:

• Direct (bolus) injection: Reconstitute with appropriate amount of Sterile Water for Injection, further dilute with approximately 5 mL, and inject slowly over 3-5 minutes
• Intermittent infusion: Dilute reconstituted solution in 50-100 mL of compatible IV fluid and infuse over 15-30 minutes 1

Compatible IV solutions:

• 0.9% Sodium Chloride
• 5% or 10% Dextrose
• 5% Dextrose in Lactated Ringer's
• 5% Dextrose and 0.9% Sodium Chloride
• 5% Dextrose and 0.45% Sodium Chloride 1

Dosage Adjustments for Renal Impairment

• CrCl ≥55 mL/min: No adjustment needed
• CrCl 35-54 mL/min: Full dose every 8 hours
• CrCl 11-34 mL/min: Half dose every 12 hours
• CrCl ≤10 mL/min: Half dose every 18-24 hours 1

Nursing Assessment and Considerations

Before Administration

1. Allergy assessment:

   • Thoroughly assess for penicillin and cephalosporin allergies
   • Note that patients with true penicillin allergy have approximately 10% cross-reactivity risk with cephalosporins 3
   • Cefazolin has a unique side chain and appears to have very low cross-reactivity with penicillins (approximately 0.7-0.8%) 3

2. Baseline assessment:

   • Obtain baseline vital signs
   • Assess renal function (BUN, creatinine, creatinine clearance)
   • Document any existing infection symptoms
   • Obtain appropriate cultures before initiating therapy 1

During Administration

1. Monitoring during infusion:

   • Observe for signs of hypersensitivity reactions (rash, urticaria, pruritus, fever, dyspnea)
   • Monitor IV site for signs of phlebitis or infiltration
   • Assess vital signs, particularly during first dose 1

2. Reconstitution and stability:

   • Reconstituted solutions are stable for 24 hours at room temperature or 10 days if refrigerated
   • Solutions may range from pale yellow to yellow without affecting potency
   • Inspect for particulate matter before administration 1

After Administration

1. Ongoing monitoring:

   • Monitor renal function regularly, especially in elderly patients
   • Assess for therapeutic response (decreased fever, improved symptoms)
   • Monitor for superinfections (oral thrush, vaginal yeast infections)
   • Watch for signs of C. difficile-associated diarrhea 1

2. Laboratory considerations:

   • May cause false-positive glucose tests with Benedict's solution, Fehling's solution, or CLINITEST tablets (not with enzyme-based tests)
   • May cause positive direct and indirect Coombs' tests 1

Special Considerations

1. Pregnancy and breastfeeding:

   • Category B: No evidence of fetal harm in animal studies
   • Present in low concentrations in breast milk; use caution 1

2. Geriatric considerations:

   • Increased risk of toxicity due to age-related decline in renal function
   • Monitor renal function closely and adjust dosage as needed 1

3. Drug interactions:

   • Probenecid may decrease renal excretion of cefazolin, increasing blood levels
   • Monitor for increased effects when used concurrently 1

Common Clinical Applications

1. Surgical prophylaxis:

   • First-line agent for most surgical procedures
   • Administer 30-60 minutes before incision
   • May continue for 24 hours postoperatively in most cases 3

2. Cardiac device implantation:

   • Recommended as prophylaxis before cardiac implantable electronic device procedures
   • Administer 1 hour before the procedure 3

3. Skin and soft tissue infections:

   • Effective for treating cellulitis and other soft tissue infections caused by susceptible organisms
   • Good tissue penetration with a tissue/serum ratio of approximately 1.06 4

By following these guidelines, healthcare providers can safely and effectively administer cefazolin while minimizing risks and optimizing therapeutic outcomes.