Treatment of Injection Site Infections
The recommended treatment for injection site infections includes incision and drainage as the primary intervention, with antibiotics only indicated when there are signs of systemic involvement or extensive local inflammation.
Diagnosis and Assessment
- Injection site infections typically present with local signs including pain, tenderness, swelling, redness, and induration 1, 2
- Evaluate for systemic signs that would indicate need for antibiotics: temperature >38.5°C, heart rate >110 beats/minute, white blood cell count >12,000/μL, or erythema extending >5 cm from the wound edge 1, 2
- Gram stain and culture of pus from abscesses are recommended to guide targeted antimicrobial therapy, though treatment without these studies is reasonable in typical cases 1
Primary Treatment Approach
- Incision and drainage is the cornerstone of treatment for injection site abscesses and infections 1, 2
- For all incisional infections, open the site, evacuate infected material, and continue dressing changes until the wound heals by secondary intention 2
- Antibiotics are NOT routinely indicated for uncomplicated injection site infections after adequate drainage 1, 2, 3
- The 90.5% cure rate observed with drainage alone (without antibiotics) in uncomplicated skin abscesses provides strong evidence that antibiotics may be unnecessary after surgical drainage 3
Antibiotic Therapy (When Indicated)
Indications for Antibiotics:
- Systemic signs of infection (fever >38.5°C, tachycardia >110 beats/minute) 1, 2
- Erythema extending >5 cm from the injection site 1, 2
- Immunocompromised patients 2
- Failure to improve after incision and drainage 1
Antibiotic Selection:
For methicillin-susceptible S. aureus (MSSA):
- First-line: Cephalexin 500 mg orally four times daily for 5-7 days 1, 4
- Alternative: Dicloxacillin or other antistaphylococcal penicillin 1
For suspected or confirmed methicillin-resistant S. aureus (MRSA):
- Trimethoprim-sulfamethoxazole (SMX-TMP) 1
- Doxycycline or clindamycin 1
- For severe infections: Vancomycin 15 mg/kg IV every 12 hours 1, 5
Special Considerations
- For injection sites near axilla or perineum, broader coverage may be needed with metronidazole plus either ciprofloxacin, levofloxacin, or ceftriaxone 1, 2
- For injection site infections following procedures involving intestinal or genital tracts, consider broader coverage with agents active against gram-negative bacteria and anaerobes 1
- If antibiotics are needed, a short course (5-7 days) is typically sufficient after adequate drainage 1, 2
- Twice-daily dosing of cephalexin (at appropriate dose adjustments) may be considered to improve medication adherence 6, 7
Prevention of Recurrence
- For patients with recurrent injection site infections (3-4 episodes per year), prophylactic antibiotics may be considered 1
- Options include oral penicillin or erythromycin twice daily for 4-52 weeks, or intramuscular benzathine penicillin every 2-4 weeks 1
- Identify and treat predisposing conditions such as edema, obesity, eczema, and other skin conditions 1
Common Pitfalls to Avoid
- Failure to perform adequate incision and drainage, which is the most important intervention 2
- Overuse of antibiotics for uncomplicated infections that would resolve with drainage alone 2, 3
- Delayed drainage leading to progression of infection 2
- Failure to recognize deeper infection that requires more aggressive intervention 2
- Not considering MRSA coverage in areas with high MRSA prevalence 1