Skin Abscess Outcomes Improve With Antibiotics Postdrainage

Diana Phillips

March 03, 2016

Adding trimethoprim-sulfamethoxazole to the follow-up for patients who undergo outpatient surgical drainage of uncomplicated superficial cutaneous abscesses improves outcomes compared with no antibiotic treatment, a study has shown.

The randomized, placebo-controlled trial reported in the March 3 issue of the New England Journal of Medicine is one of the first to demonstrate a benefit of adjunctive antibiotics for postdrainage abscess management since the emergence of community-associated methicillin-resistant Staphylococcus aureus (MRSA), according to lead investigator David A. Talen, MD, from the Department of Emergency Medicine, Olive View–UCLA Medical Center, Los Angeles, California, and colleagues.

Of 1265 patients with a drained cutaneous abscess enrolled from five US emergency departments, those who were treated twice daily with 320 mg trimethoprim and 1600 mg sulfamethoxazole for 7 days had a higher cure rate and better secondary outcomes, including fewer subsequent surgical drainage procedures, new skin infections, and infections spread among household members, than those who received placebo, the authors report.

"We found that the cure rate with respect to the primary lesion was approximately 7 percentage points higher with trimethoprim–sulfamethoxazole than with placebo," the authors write.

Specifically, the abscess cure rate in the treatment group was 80.5% compared with 73.6% in the modified intention-to-treat 1 (mITT-1) population, which included patients who took at least a single dose of the treatment or placebo and had an interview through the test-of-cure visit (14 - 21 days after drainage; difference, 6.9 percentage points; 95% confidence interval, 2.1 - 11.7 percentage points; P = .005). The analysis also included patients who withdrew from the trial, were lost to follow-up before final classification, or had missing outcomes.

"If we assumed that all participants in the mITT-1 population who were lost to follow-up (58 in the trimethoprim–sulfamethoxazole group and 39 in the placebo group) had a clinical cure rather than clinical failure, the cure rates would be 89.7% and 79.9%, respectively," the authors write.

The median length, width, and depth, respectively, of patients' primary lesions was 2.5, 2.0, and 1.5 cm, and the median length and width of erythema were 6.5 and 5.0 cm, respectively. Abscess cultures identified MRSA in 45.3% of the mITT-1 population, and of the MRSA isolates, 97.4% were susceptible to trimethoprim-sulfamethoxazole.

A comparison of cure rates for patients in the mITT populations and those for whom response was assessed at 48 to 72 hours (the US Food and Drug Administration guidance early end-point population [i.e., participants in]) showed no significant difference between outcomes for drainage alone and adjunctive antibiotics.

Secondary outcomes in patients observed through the test-of-cure visit indicate that trimethoprim-sulfamethoxazole, relative to placebo, was associated with lower rates of subsequent surgical drainage procedures (3.4% vs 8.6%), skin infections at a new site (3.1% vs 10.3%), and infections among household members (1.7% vs 4.1%).

"Overall rates of adverse events were similar in the trimethoprim–sulfamethoxazole group and the placebo group, and most events were considered to be mild," the authors report. Gastrointestinal effects were most commonly reported, but there were no cases of Clostridium difficile colitis. No significant differences were observed in treatment discontinuation resulting from adverse events, and no treatment-associated serious or life-threatening adverse events occurred.

The findings suggest that oral treatment with trimethoprim-sulfamethoxazole, which is inexpensive and appears to be safe, according to the authors, "offers the possibility of lower rates of costly subsequent medical visits, surgeries, and hospitalizations and of new infections among patients and their household contacts."

According to current practice guidelines, drainage is sufficient abscess treatment for many patients, whereas adjunctive antibiotics are recommended for patients who have certain clinical or demographic characteristics, including an infected site with a diameter of more than 5 cm. Although participants in the current trial had generally small abscesses, "most participants had a total lesion size, including associated erythema, of more than 5 cm, and many met other guideline criteria for antibiotic treatment," the authors observe.

This study was supported by a grant from the National Institute of Allergy and Infectious Diseases. Dr Talen disclosed financial relationships with Actavis and Cempra. Other coauthors report financial or other relationships with Cempra, Summit Therapeutics, Tetraphase Pharmaceuticals, Janssen, Merck, the Medicines Company, Cepheid, Durata Therapeutics, and Cubist Pharmaceuticals.

N Engl J Med. 2016:374:823-32. Abstract

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