Uncomplicated Skin Abscess

Posted by • March 4th, 2016

2016-03-03_14-22-56Between 1993 and 2005, annual emergency department visits for skin and soft-tissue infections in the United States increased from 1.2 million to 3.4 million, primarily because of an increased incidence of abscesses. The primary treatment of a cutaneous abscess is drainage. Whether adjunctive antibiotics lead to improved outcomes in patients with uncomplicated abscesses or just more cost and side effects is unclear. Talan et al. conducted a randomized trial at five U.S. emergency departments to determine whether trimethoprim–sulfamethoxazole would be superior to placebo in outpatients older than 12 years of age who had an uncomplicated abscess that was being treated with drainage. The primary outcome was clinical cure of the abscess, assessed 7 to 14 days after the end of the treatment period.

In this randomized clinical trial in patients presenting to U.S. emergency departments with an acute uncomplicated cutaneous abscess, drainage plus trimethoprim–sulfamethoxazole therapy for a week was associated with modest clinical benefits as compared with drainage alone. A new Original Article summarizes.

Clinical Pearl

• Have previous investigations shown a benefit of adjunctive antibiotics for uncomplicated skin abscess?

Previous investigations, which had small numbers of participants, did not show a benefit of antibiotic treatment. Larger studies are required to show relatively small differences in cure rates, because drainage alone may result in resolution in more than 80% of cases.

Clinical Pearl

• What are current practice guidelines regarding the adjunctive use of antibiotics for uncomplicated skin abscesses?

Practice guidelines for abscess treatment state that drainage is sufficient for many patients and, primarily on the basis of expert opinion, recommend adjunctive antibiotics for patients who have certain clinical or demographic characteristics, including the systemic inflammatory response syndrome, diabetes, very young or very old age, an infected site with a diameter of more than 5 cm, and surrounding cellulitis.

Morning Report Questions

Q: Do adjunctive antibiotics lead to an improved cure rate in patients with uncomplicated skin abscess?

A: In the study by Talan et al. involving 1265 patients with a drained cutaneous abscess, the authors found that patients who received trimethoprim–sulfamethoxazole (at doses of 320 mg and 1600 mg, respectively, twice daily, for 7 days) had a higher cure rate than those who received placebo. The abscess cure rate was 80.5% in the trimethoprim–sulfamethoxazole group and 73.6% in the placebo group in the modified intention-to-treat 1 population (difference, 6.9 percentage points; 95% confidence interval [CI], 2.1 to 11.7; P=0.005). The authors also found that many secondary outcomes were better in the trimethoprim–sulfamethoxazole group than in the placebo group, including fewer subsequent surgical drainage procedures, new skin infections, and infections among household members through 6 to 8 weeks after the end of the treatment period. Participants who received trimethoprim–sulfamethoxazole had only slightly more gastrointestinal side effects (mostly mild) than those who received placebo and had no serious or life-threatening drug-related adverse reactions.

Table 2. Baseline Characteristics in the Modified Intention-to-Treat 1 Population.

Table 3. Cure Rates among Patients with a Drained Cutaneous Abscess in Three Trial Populations.

Table 4. Secondary Outcomes in the Per-Protocol Population.

Q: How would you interpret the results of the study by Talan et al.?

A: Talan et al. found that the cure rate with respect to the primary lesion was approximately 7 percentage points higher with trimethoprim–sulfamethoxazole than with placebo. Thus, adjunctive oral treatment with trimethoprim–sulfamethoxazole — which is inexpensive, appears to be safe, and is associated with a higher cure rate of the primary lesion than that with placebo — offers the possibility of lower rates of costly subsequent medical visits, surgeries, and hospitalizations and of new infections among patients and their household contacts. On the other hand, drainage alone was associated with a similar rate of early response at 48 to 72 hours and a high overall cure rate. Trimethoprim–sulfamethoxazole can cause uncommon but serious complications such as Clostridium difficile colitis, renal and electrolyte problems, drug interactions, and rare life-threatening reactions (e.g., Stevens–Johnson syndrome, at an estimated rate of 3 cases per 100,000 exposed persons). Increased antibiotic use may promote bacterial resistance. A similar National Institutes of Health–funded trial (ClinicalTrials.gov number, NCT00730028) may also shed light on the efficacy of adjunctive antibiotics.

To Learn more about skin abscess, please read a new Clinical Decisions.

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