What is an intravenous (IV) antibiotic option for a healthy patient with a stab wound to the knee and no known antibiotic allergies?

IV Antibiotic Options for Stab Wound to the Knee

For a healthy patient with a stab wound to the knee, cefazolin 1-2g IV every 8 hours is the recommended intravenous antibiotic, targeting methicillin-susceptible Staphylococcus aureus (MSSA) and streptococci, which are the primary pathogens in skin and soft tissue infections. 1

Primary IV Antibiotic Recommendation

• Cefazolin 1g IV every 8 hours is the first-line parenteral agent for MSSA skin and soft tissue infections (SSTIs), including traumatic wounds 1
• Cefazolin provides excellent coverage against the most common pathogens in penetrating knee injuries: Staphylococcus aureus and Streptococcus species 1
• This dosing achieves adequate tissue penetration, with tissue/serum drug concentration ratios of approximately 1.06, ensuring therapeutic levels at the wound site 2

Alternative IV Options

For Penicillin/Cephalosporin Allergy:

• Clindamycin 600mg IV every 8 hours is the recommended alternative for patients with beta-lactam allergies (except immediate hypersensitivity reactions) 1
• Vancomycin 30mg/kg/day divided in 2 doses IV is reserved for patients with immediate hypersensitivity reactions to beta-lactams 1
  • Vancomycin infusion must be administered over 120 minutes and should be completed ideally 30 minutes before any surgical intervention 1

If MRSA is Suspected:

• Vancomycin 30mg/kg/day in 2 divided doses IV is the parenteral drug of choice for MRSA SSTIs 1
• Linezolid 600mg IV every 12 hours provides bacteriostatic coverage with no cross-resistance to other antibiotic classes 1
• Daptomycin 4mg/kg IV every 24 hours offers bactericidal activity against MRSA 1
• Ceftaroline 600mg IV twice daily is a newer bactericidal option with MRSA coverage 1

Duration of Therapy

• For uncomplicated traumatic wounds without exposed hardware or joint involvement, treatment duration is typically 3-5 days 3
• If there is concern for joint involvement or exposed structures, duration may extend to 4-6 weeks IV therapy depending on surgical findings 3
• Reassess clinical response at 4 weeks; if no improvement, consider surgical consultation 3

Important Clinical Considerations

• Cefazolin is contraindicated in patients with known cephalosporin allergy 4
• The Infectious Diseases Society of America guidelines emphasize that antibiotic selection should be based on whether systemic signs of infection (SIRS criteria) are present: temperature >38°C or <36°C, tachypnea >24 breaths/min, tachycardia >90 beats/min, or WBC >12,000 or <4,000 cells/μL 1
• For simple traumatic wounds without systemic toxicity, oral antibiotics may be sufficient after initial IV dosing 1
• Vancomycin should be reserved for specific indications: beta-lactam allergy, known/suspected MRSA colonization, or recent antibiotic therapy 5

Dosing Adjustments

• Standard cefazolin dosing is 1g IV every 8 hours, but can be increased to 2g every 8 hours for severe infections 1
• Cefazolin requires renal dose adjustment: for creatinine clearance 40-70 mL/min, reduce to 60% of normal dose; for 20-40 mL/min, reduce to 25% of normal dose 4