title: In vivo antibacterial effects of tretinoin-clindamycin and clindamycin alone on Propionibacterium acnes with varying clindamycin minimum inhibitory.
abstract: 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.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  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).
  
  
  CONCLUSIONS
  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).
authors: Department of Dermatology, University of Pennsylvania, Philadelphia, PA, USA. jjleyden@mindspring.com
authors: James J
authors: JJ
authors: Leyden
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D058491:Bacterial Load; D002981:Clindamycin / Q000494:pharmacology*; D004338:Drug Combinations; D004352:Drug Resistance, Microbial; D004917:Erythromycin / Q000494:pharmacology; D005260:Female; D006801:Humans; D007641:Keratolytic Agents / Q000494:pharmacology*; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D011425:Propionibacterium acnes / Q000187:drug effects*; D012867:Skin / Q000382:microbiology; D014212:Tretinoin / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D007641:Keratolytic Agents; D002981:Clindamycin; D014212:Tretinoin; D004917:Erythromycin