Trimethoprim/sulfamethoxazole (TMP/SMX) and clindamycin are frequently prescribed to treat cellulitis. The primary objective was to determine if weight-based dosing of these antibiotics is associated with better outcomes in cellulitis. The secondary objective was to assess variables associated with clinical failure among hospitalized patients with cellulitis with or without cutaneous abscess.

This multi-center retrospective cohort study was conducted from January 1, 2010 to September 4, 2014. Adult patients admitted for cellulitis who received a minimum of seven days of therapy and discharged on oral clindamycin or TMP/SMX were included. Binary univariate and multivariate logistic regression analyses were performed to identify risk factors for clinical failure, including the impact of dose adequacy of clindamycin and TMP/SMX on clinical outcomes.

A total of 208 cases met inclusion criteria. Of these cases, 120 (57.7%) received inadequate dosing of clindamycin (<10 mg/kg/day) or TMP/SMX (<5 mg TMP/kg per day) while 88 (42.3%) received adequate dosing. Clinical failure occurred in 36/120 (30%) and 15/88 (17%) of patients receiving inadequate and adequate doses, respectively (p = 0.032). Upon univariate analysis length of stay ≥ 7 days (OR = 2.96, p = 0.046) and inadequate dosing (OR = 2.09, p = 0.034) were associated with clinical failure. Upon multivariate analysis, inadequate dosing was independently associated with clinical failure (OR = 2.01, p = 0.032).

Inadequate dosing of clindamycin and TMP/SMX is independently associated with clinical failure in patients hospitalized with cellulitis. Further prospective studies evaluating weight-based dosing of clindamycin and TMP/SMX in the setting of cellulitis are warranted.