Activation of clindamycin phosphate by human skin

Aims: To investigate the relative antimicrobial activity of clindamycin pho sphate (CP) and clindamycin (Cly) and to examine the effect of skin homogen ates on the activity of CP. Methods and Results: Minimum inhibitory concentrations (MIC) were determine d against dermally relevant organisms and bactericidal activity was studied using time-kill methodology. The effect of skin homogenates on the antimic robial activity of CP was studied by well-diffusion assay. The MIC of Cly w as substantially lower than that of CP in all susceptible organisms. Clinda mycin also showed greater bactericidal activity (rate of kill) than CP. Pho sphatases in skin homogenates activated CP at pH 4-8 with a maximal activat ion at pH 4. Conclusions: Phosphatases within the skin have been shown to convert CP to the more potent form Cly. Significance and Impact of the Study: Conversion to Cly is a major determin ant of antimicrobial activity in the skin layers following topical applicat ion of CP.