#227 There’s Pus About, So Are Antibiotics In or Out? Adding antibiotics for abscess management

CLINICAL QUESTION

QUESTION CLINIQUE

Does the addition of antibiotics to incision and drainage improve cure rates in single, uncomplicated skin abscesses?

BOTTOM LINE

RÉSULTAT FINAL

Adding antibiotics that cover MRSA during incision and drainage for a small abscess increases the cure rate from 85% to 92%, meaning an additional one in 15 patients will be cured compared to placebo at one month. Approximately 25% of patients will experience adverse effects, with gastrointestinal adverse effects occurring for an additional one in 11 on clindamycin and one in 50 on trimethoprim-sulfamethoxazole, compared to placebo.

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EVIDENCE

DONNÉES PROBANTES

Two recent systematic reviews, including four and 14 randomized controlled trials (RCTs), 2,406 and 4,198 patients, respectively.^1,2 Results statistically significant unless mentioned.

Both relied heavily on two new high-quality RCTs (2,051 patients) of clindamycin or trimethoprim-sulfamethoxazole in adults and children with single abscesses <5 cm that had undergone incision and drainage.^3,4 Prevalence of MRSA ~45%.
Treatment failure at one month example:² 8% versus 15% placebo, Number Needed to Treat (NNT)=15.
- If limited to trials without MRSA coverage, no longer statistically significant.²
Recurrence or new lesion within one month example:² 8% versus 15% (placebo), NNT=15.
- At 1-3 months:² 18% versus 25%, NNT=14.
Subgroup analysis demonstrated benefit with antibiotics that cover MRSA, but not those without (example: cephalexin).²
Total adverse effects:¹ 25% versus 22% (placebo), Number Needed to Harm (NNH)=38.
- Gastrointestinal adverse effects:²
  - Clindamycin: ~10% more than placebo, NNH=11.
  - Trimethoprim-sulfamethoxazole: 2% more than placebo, NNH=47.
Limitations: One systematic review only included studies of antibiotics that have activity against MRSA;¹ only two studies included patients with diabetes (2.4% and 11% of study populations, respectively).²

Context:

Older systematic reviews^5,6 and guidelines⁷ found no improvement when antibiotics added to incision and drainage but did not include the newest RCTs above.
Antibiotics are recommended with systemic illness, extensive tissue damage or at risk of poor healing or complications (examples: immunocompromised or prosthetic device).⁸
Perirectal, perineal, and paronychial abscesses, or sites requiring specialized management, excluded from above RCTs.^3,4
Risk factors for community-acquired MRSA include recent antibiotic use, contact sports, group housing, lower socioeconomic status, and IV drug use.⁹