In Vivo Antibacterial Effects of Tretinoin-Clindamycin and Clindamycin Aloneon Propionibacterium acnes With Varying Clindamycin Minimum InhibitoryConcentration Levels
December 2012 | Volume 11 | Issue 12 | Original Article | 1434 | Copyright © December 2012
James J. Leyden MD
Department of Dermatology, University of Pennsylvania, Philadelphia, PA
Objective: To quantify the antimicrobial effect of clindamycin phosphate 1.2% and tretinoin 0.025% gel and 1% clindamycin phosphate
gel in patients with Propionibacterium acnes of varying sensitivity to clindamycin.
Design: Study 1 was an initial range-finding study that was neither blinded nor randomized. Study 2 was an open-label, randomized, splitface, single-center study. Both studies were conducted in Pennsylvania.
Patients: Study 1 (n=20) and study 2 (n=22) involved healthy patients aged 18 years or older with initial P acnes levels ≥104/cm2 and minimum inhibitory concentrations (MICs) ≥8 µg/mL for clindamycin.
Interventions: Study 1, clindamycin gel applied twice daily for 6 weeks. Study 2; once-daily application with the combination gel to one cheek and clindamycin gel to the other side for 6 weeks.
Main Outcome Measure: The comparative effectiveness of each product vs P acnes of varying sensitivity to clindamycin at 3 and 6 weeks posttreatment.
Results: For study 1, at 3 and 6 weeks, clindamycin-treated patients with MICs of ≤256 µg/mL showed greater reductions than those with MICs ≥512 µg/mL (P=.0001). Study 2 showed a significant reduction in P acnes for both products, with no differences found. Clindamycin alone was more effective in vivo in patients with MIC levels of ≤256 µg/mL than patients with higher MIC levels. The combination product produced a greater reduction than clindamycin alone after 6 weeks in patients with high MICs >512 µg/mL (P=.0047).
Conclusion: These studies suggest that 1% clindamycin alone produces a varying in vivo antimicrobial effect, with a breakpoint at ≤256 µg/mL. Use of clindamycin phosphate 1.2% and tretinoin 0.025% gel resulted in a significantly greater in vivo antimicrobial effect than clindamycin alone in patients carrying P acnes with MICs of ≥512 µg/mL (P=.0047).
J Drugs Dermatol. 2012;11(12):1434-1438.