In summary, for patients who received adjuvant antibiotic therapy after incision and drainage:

Benefits in NNT

  • 7.4% reduced risk of treatment failure
  • 10.0% reduced risk of recurrence
  • 1 in 14 were helped (treatment failure prevented)
  • 1 in 10 were helped (recurrence prevented)

Harms in NNT

    4.4% higher risk of adverse events
    1 in 23 were harmed (experienced adverse events)

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Source: Gottlieb M, Demott JM, Hallock M, Peksa GD. Systemic Antibiotics for the Treatment of Skin and Soft Tissue Abscesses: A Systematic Review and Meta-Analysis. Annals of Emergency Medicine 2019;73(1):8–16.

Study Population: Four studies with 2406 adults and children undergoing incision and drainage for cutaneous abscess.

Efficacy Endpoints: Treatment failure, recurrence

Harm Endpoints: Adverse events, diarrhea

Narrative: Annually more than 3 million patients present to U.S. emergency departments (EDs) with cutaneous abscess, a number that has been increasing.1 Standard treatment involves incision and drainage (I&D), while routine use of systemic antibiotics after incision and drainage is controversial. Recently, two large studies found increased cure rates with systemic antibiotics after I&D compared to placebo.2, 3 The goal of the systematic review summarized here is to provide updated evidence on the efficacy of systemic antibiotics with activity against methicillin-resistant Staphylococcus aureus after I&D of cutaneous abscess.4

The review identified four randomized trials comprised of 2406 adult and pediatric subjects who presented with acute, simple, cutaneous abscesses that required I&D. Three took place exclusively in the ED and one in a mix of ED and outpatient settings. In three trials, participants were randomized to receive trimethoprim–sulfamethoxazole (TMP-SMX) or placebo while one trial randomized participants to receive TMP-SMX, clindamycin, or placebo. The primary outcome was treatment failure within 21 days based on clinical assessment and the need for further intervention. Secondary outcomes were recurrence, overall adverse events (gastrointestinal symptoms, rashes, and generalized symptoms), and diarrhea.

Antibiotic therapy was associated with an increased rate of clinical cure (absolute risk difference [ARD]: 7.4%; odds ratio [OR] 2.3; 95% confidence interval [CI], 1.8 - 3.1; NNT 14) and a reduced risk of recurrence (ARD: 10%; OR: 0.3; CI: 0.2 - 0.4; NNT: 10). Antibiotic therapy was also associated with an increase in adverse events (ARD: 4.4%; OR: 1.3; CI: 1.1 - 1.6; NNH: 23) but no significant change in diarrhea.

Caveats: Caveats: The quality of evidence was high, risk of bias was low, and there was no significant heterogeneity. Additionally, another systematic review and meta-analysis, which included RCTs of antibiotics without activity against MRSA, reached the same conclusions as the authors of this analysis.5 There are however limitations. One limitation is that I&D technique was not standardized in two of the studies.6, 7 This is unlikely to have affected the outcome since I&D is a simple procedure and the two studies that did standardize the I&D technique both nonetheless demonstrated a benefit to antibiotics.2, 3 Another is that two different antibiotics (TMP-SMX and clindamycin) and multiple dosing regimens were used, though the clinical cure rate between antibiotics was not different.3 Additionally, the studies were not powered to detect rare adverse events such as severe allergic reactions and Clostridium difficile infection. Finally, there was variation in follow-up period with three studies assessing patient outcomes at 7-10 days, and the fourth study assessing outcomes at 14-21 days.4

Notably, the clinical cure rate without antibiotics was 84% compared to 92% with antibiotics, and treatment failure rarely results in life-threatening complications or even hospitalization—usually just a return visit with an additional I&D and outpatient antibiotics. The slightly increased clinical cure rate must be balanced against the harms associated with antibiotic use including adverse events and antibiotic resistance.8, 9 The harms that would be caused to the community by increasing antibiotic resistance may outweigh the benefits to the individual in many cases.

In summary, adjuvant antibiotics given routinely after I&D of cutaneous abscesses were associated with increased clinical cure, decreased recurrence, and increased adverse events in this review. The benefits should be weighed against the adverse events, the cost of treatment failure, and the impact on society of increasing antibiotic usage. Based on the continued necessity for clinicians to weigh the benefits and harms of adjuvant antibiotics, the most appropriate rating is Yellow (benefits and harms should be individualized).

The original manuscript was published in Academic Emergency Medicine as part of the partnership between TheNNT.com and AEM.

Author: John Conway, BS; Benjamin Friedman, MD
Supervising Editor: Shahriar Zehtabchi, MD

Published/Updated: December 3, 2019

  1. The Title Bar

    The title bar is color-coded with our overall recommendation.

    • Green: Benefits outweigh risks.
    • Yellow: Unclear risk/benefit profile.
    • Red: Benefits do not outweigh risks.
    • Black: Obvious harms, no clear benefits.
  2. Tip content...