Adding an antibiotic to uncomplicated I&Ds may improve outcomes

- Jennifer Middleton, MD, MPH

Adding an oral antibiotic after incision and drainage of an uncomplicated skin abscess has been found, to date, to not improve clinical outcomes. The American College of Emergency Physicians (ACEP) even has a Choosing Wisely recommendation to this effect. A study published last week, however, found differently: adding an antibiotic after incision and drainage (I&D) of small skin abscesses resulted in better clinical healing.

The study authors prospectively enrolled 505 adults and 281 children at several sites across the United States who presented to urgent care clinics, Emergency Departments (EDs), and outpatient care sites with small skin abscesses (no greater than 5 cm in diameter for adults, no larger than 3 cm for children under 1 year of age, no larger than 4 cm for children aged 1-8 years) and randomized them to receive, after incision and drainage, either 10 days of clindamycin, trimethoprim/sulfamethoxazole (TMP/SMX), or placebo. 81.7% and 83.1% of the participants who received clindamycin or TMP/SMX, respectively, had a clinical cure 10 days after completing antibiotics, compared with only 68.9% of participants who received a placebo (95% confidence intervals 78.3-87.9, 76.8-86.7, and 62.9-74.9, respectively). When analyzed separately, the researchers found that clindamycin was more effective in the pediatric participants compared to TMP/SMX, while the difference between cure rates for adults for these 2 antibiotics was not significant.

New infections in the 30 days following treatment were more common in the placebo group than either antibiotic group; clindamycin was more effective than TMP/SMX in preventing recurrent infection, especially in pediatric participants. Adverse events were more common in the clindamycin group, though, and most commonly consisted of diarrhea and nausea; these were described as "mild or moderate and resolved without sequelae." 1 hypersensitivity reaction to TMP/SMX was described.

This study's findings contradict common practice and the ACEP's Choosing Wisely recommendation. A closer look at the references cited in the ACEP's Choosing Wisely recommendation, however, demonstrate that the evidence to date regarding treatment of uncomplicated skin abscesses has been a bit meager. They include a smaller randomized control trial (RCT) from 2010 that found placebo equivalent to TMP/SMX in 161 pediatric patients treated in EDs for uncomplicated abscesses; an RCT from 1985 that enrolled 50 adults and found no difference in clinical improvement between those treated with cephradine (a first-generation cephalosporin) and placebo; and, a 2011 cross-sectional study that examined differences in antibiotic prescribing habits across 3 separate pediatric EDs but did not examine clinical outcomes.

Additionally, the Infectious Diseases Society of America's 2014 Practice Guideline for the Diagnosis and Management of Skin and Soft Tissue Infections includes a "strong" recommendation against using antibiotics in uncomplicated skin abscesses but describes the quality of the evidence supporting this recommendation as "low." The more robust design of this new study, with its large number of participants and breath of geographic sites, makes its findings difficult to dismiss. It also builds on a 2016 RCT which found that, in care sites with a high prevalence of methicillin-resistant Staphylococcus aureus (MRSA), adding TMP/SMX to incision and drainage improved clinical cure rates in adults and teens with uncomplicated skin abscesses compared to placebo.

Given all of the attention on inappropriate antibiotic use these last few weeks on the blog, it's admittedly a bit tough to digest a study that suggests adding antibiotic treatment to a condition that didn't previously warrant it. It will be interesting to see if other researchers attempt to replicate this result or, perhaps, perform a systematic review of all of the data on this topic.

Will this study change how you care for patients after incision and drainage of an uncomplicated skin abscess?