Clinical Trial: Comparative Effectiveness of Cephalexin Plus Trimethoprim- Sulfamethoxazole Versus Cephalexin Alone for Treatment of Uncomplicated Cellulitis: A Randomized Controlled Trial

Background. Community-associated methicillin-resistant S. aureus (CA-MRSA) is the most common organism isolated from purulent skin infections. Antibiotics are usually not beneficial for skin abscess, and national guidelines do not recommend CA-MRSA coverage for cellulitis, except purulent cellulitis, which is uncommon. Despite this, antibiotics targeting CA-MRSA are prescribed commonly and increasingly for skin infections, perhaps due, in part, to lack of experimental evidence among cellulitis patients. We test the hypothesis that antibiotics targeting CA-MRSA are beneficial in the treatment of cellulitis. Methods. We performed a randomized, multicenter, double-blind, placebo-controlled trial from 2007 to 2011. We enrolled patients with cellulitis, no abscesses, symptoms for <1 week, and no diabetes, immunosuppression, pe-ripheral vascular disease, or hospitalization (clinicaltrials.gov NCT00676130). All participants received cephalexin. Additionally, each was randomized to trimethoprim-sulfamethoxazole or placebo. We provided 14 days of antibiot-ics and instructed participants to continue therapy for ≥1 week, then stop 3 days after they felt the infection to be cured. Our main outcome measure was the risk difference for treatment success, determined in person at 2 weeks, with telephone and medical record confirmation at 1 month. Results. We enrolled 153 participants, and 146 had outcome data for intent-to-treat analysis. Median age was 29, range 3–74. Of intervention participants, 62/73 (85%) were cured versus 60/73 controls (82%), a risk differenc