Original Research

Lack of Significant Anti-inflammatory Activity With Clindamycin in the Treatment of Rosacea: Results of 2 Randomized, Vehicle-Controlled Trials

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Safety Evaluation

Safety was assessed by the incidence of adverse events (AEs).

Statistical Analysis

Studies were powered assuming 60% reduction in inflammatory lesion counts with active and 40% with vehicle, based on historical data from a prior study with metronidazole cream 0.75% versus vehicle; 64 participants were required in each treatment group to detect this effect using a 2-sided t test (α=.017). Pairwise comparisons (clindamycin vs respective vehicle) were performed using the Cochran-Mantel-Haenszel test for combined lesion count percentage change.

Results

Participant Disposition and Baseline Characteristics

Overall, a total of 629 participants were randomized across both studies. In study A, a total of 416 participants were randomized into 5 treatment arms, with 369 participants (88.7%) completing the study; 47 (11.3%) participants discontinued study A, mainly due to participant request (19/47 [40.4%]) or lost to follow-up (11/47 [23.4%]). In study B, a total of 213 participants were randomized to receive either clindamycin gel 1% (n=109 [51.2%]) twice daily or vehicle gel (n=104 [48.8%]) twice daily, with 193 participants (90.6%) completing the study; 20 (9.4%) participants discontinued study B, mainly due to participant request (6/20 [30%]) or lost to follow-up (4/20 [20%]). Participants in studies A and B were similar in demographics and baseline disease characteristics (Table). The majority of participants were white females.

Efficacy

No statistically significant difference was observed in all pairwise comparisons (clindamycin cream twice daily vs vehicle twice daily, clindamycin cream once daily vs vehicle once daily, clindamycin gel vs vehicle gel) for the primary end point of mean percentage change from baseline in inflammatory lesion counts at week 12 (Figure 1; P>.5 for all pairwise comparisons).

Figure 1. Mean percentage decrease from baseline in total inflammatory lesion count for clindamycin cream 1% twice daily (n=81) versus vehicle cream twice daily (n=81)(A), clindamycin cream 1% once daily (n=87) and clindamycin cream 0.3% once daily (n=85) versus vehicle cream once daily (n=82)(B), and clindamycin gel 1% twice daily (n=109) versus vehicle gel twice daily (n=104)(C). All P values were not significant.

At week 12, the proportion of participants in study B deemed as a success (none/clear or mild/almost clear [investigator global rosacea severity score of 0 or 1]) in the clindamycin gel 1% and vehicle gel groups were 45% versus 38%, respectively (P=.347) (Figure 2).

Figure 2. Study B success rate (score of 0 [none/clear] or 1 [mild/almost clear]) of participants after 12 weeks of treatment with clindamycin gel 1% twice daily or vehicle gel twice daily based on the 5-point investigator global rosacea severity score (P=.347).

For the secondary end point of mean investigator global rosacea severity assessment at week 12 (study A), there were no significant differences between the active and vehicle control groups (P>.5 for all pairwise comparisons)(Figure 3). Also, the proportion of participants with at least a moderate investigator global improvement assessment from baseline to week 12 ranged from 45% for clindamycin cream 1% twice daily to 56% for clindamycin cream 0.3% cream once daily and from 45% for vehicle cream once daily to 51% for vehicle cream twice daily (P>.5 for all pairwise comparisons).

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