Increased therapeutic failure for cephalexin versus comparator antibiotics in the treatment of uncomplicated outpatient cellulitis.

We reviewed records of outpatients to determine the therapeutic failure rate of cephalexin in treating uncomplicated cellulitis. Therapeutic failure was defined as an increase in antibiotic dosage, prescription renewal, or addition or substitution of another antibiotic. Demographics, physical characteristics, risk factors, intervention, and outcome data were collected. Twenty-seven percent of patients failed therapy with an oral antibiotic. The failure rate for cephalexin was 40% versus 20% for comparator antibiotics (p=0.02, odds ratio [OR] 2.62, 95% confidence interval [CI] 1.18-5.75). We identified no statistically significant variables related to cephalexin failure. Concomitant acid suppressive therapy was administered with cephalexin in 42% of failures and 20% of nonfailures (p=0.11, OR 2.78, 95% CI 0.77-9.87). These data suggest that cephalexin's efficacy was less than that of other antimicrobials in treating cellulitis, possibly related to concurrent acid suppression.