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Trimethoprim–Sulfamethoxazole for Uncomplicated Skin Abscess

Three Part Question

In [patients with uncomplicated skin abscesses who have undergone abscess incision and drainage], does [treatment with oral trimethoprim-sulfamethoxazole compared to placebo] [reduce treatment failure at 7 days]?

Clinical Scenario

A man aged 21 years presents to the ED with a 3-day history of increasing redness, swelling and pain in his right thigh. On examination there is an area of fluctuance, approximately 3 cm in diameter, with associated tenderness, on the right anterior thigh. Erythema extends approximately 1 cm beyond the edges of the fluctuance. As the emergency physician, you incise and drain the abscess. You wonder whether a 7-day course of trimethoprim-sulfamethoxazole is really necessary in a healthy person, despite the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections.

Search Strategy

Medline 1966-10/16 using NHS evidence: [(exp trimethoprim sulfamethoxazole/) AND (exp abscess/)] limit to humans and English language 197 records.

The Cochrane Library date of searching 13/10/16: MeSH descriptor: (Trimethoprim, Sulfamethoxazole Drug Combination) explode all trees AND MeSH descriptor: (Abscess) explode all trees 19 records 0 unique articles.

Search Outcome

ne hundred and ninety-seven papers were identified using the searches reported above, of which 14 were relevant and 3 were randomised clinical studies that addressed the clinical question. These three randomised trials are summarised in the table

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Talan et al
United States
1247 of 1265 patients 12 years and older who presented with uncomplicated abscess treated with drainage in five US EDs Incision and drainage with placebo or incision and drainage with oral trimethoprim-sulfamethoxazoleMulticentre double-blind, placebo-controlled RCTClinical cure of abscess at 7 days73.6% vs 80.5% Difference 6.9% (95 CI 2.1% to 11.7%, p=0.005)High treatment dose of trimethoprim-sulfamethoxazole (320 and 1600 mg compared with usual 160 and 800 gm Degree of non-adherence in trial May not be applicable if abscess is not fully drained. Training provided for this RCT May not be applicable if abscess is not fully drained. Training provided for this RCT
Schmitz et al
United Statates
190 of 212 patients, 16 and older, with uncomplicated abscess Incision and drainage with placebo or incision and drainage with oral trimethoprim-sulfamethoxazoleDouble-blind, placebo-controlled RCTTreatment failure at 7 days New lesions at 30 days26% vs 17% (p=0.12) 28% vs 9% (p=0.02)Loss of follow-up Only healthy adults enrolled No standardisation of incision and drainage technique
Duong et al,
United States
161 patients, aged 3 months to 18 years Incision and drainage with placebo or incision and drainage with oral trimethoprim-sulfamethoxazoleDouble blind, randomized, controlled trialTreatment failure after 10 days of eitherNo difference between two groupsBias: selection 7% lost to follow-up 40% of follow-ups by phone calls
New lesion development at 10 days26.4% vs 12.9%


There are numerous reports indicating a dramatic increase in skin infections caused by community-acquired MRSA. Surgical drainage of skin abscesses has been the accepted standard treatment. With the emergence of MRSA infections, antibiotics are often recommended after incision and draining. Of the three clinical studies found, only one described improved cure rates of the abscess after treatment with trimethoprim-sulfamethoxazole. However, all three papers describe a decrease in new abscess formation after treatment.

Editor Comment

RCT, randomised controlled trial.

Clinical Bottom Line

Trimethoprim-sulfamethoxazole may help with abscess cure, and will decrease abscess formation at new sites.


  1. Talan DA, Mower WR, Krishnadasan A, et al. Trimethoprim–Sulfamethoxazole versus Placebo for Uncomplicated Skin Abscess. NEJM 2016;374:823–32.
  2. Schmitz GR, Bruner D, Pitotti R, et al. Randomized Controlled Trial of Trimethoprim-Sulfamethoxazole for uncomplicated Skin Abscesses in Patients at Risk for Community-Associated MRSA Infection Ann Emerg Med 2010; 56:283-287.
  3. Duong M, Markwell S, Peter J, et al. Randomized, Controlled Trial of Antibitoics in the Management of Community-Acquired Skin Abscesses in the Pediatric Patient Ann Emerg Med 2010;55: 401–7.