Influence of Bile Acids on Clindamycin Hydrochloride Skin Permeability: In Vitro and In Silico Preliminary Study.

Background and objective: Topical clindamycin formulations are widely used in clinical practice, but poor bioavailability and restricted skin penetration considerably limit their therapeutic efficacy. Penetration enhancement represents a promising and rational strategy to overcome the drawbacks of conventional topical pharmaceutical formulations. We aim to assess the influence of cholic acid (CA) and deoxycholic acid (DCA) on the permeability of clindamycin hydrochloride by performing the in vitro skin parallel artificial membrane permeability assay (skin-PAMPA) at two relevant pH values (5.5 and 6.5) and the interactions of tested substances with skin ATP-binding cassette (ABC) transporters in silico.

Methods: After the incubation period, the clindamycin hydrochloride concentrations in both compartments were determined spectrophotometrically, and the apparent permeability coefficients (P_app) were calculated. Vienna LiverTox web service was used to predict the interactions of clindamycin and bile acids with potential drug transporters located in human skin.

Results: Both CA and DCA at the highest studied concentration of 100 μM in the tested solutions increased the skin-PAMPA membrane permeability of clindamycin hydrochloride. This effect was more pronounced for CA and at a higher studied pH value of 6.5, which is characteristic of most dermatological indications treated with topical clindamycin preparations. Clindamycin transport may also be mediated by ABC transporters located in skin and facilitated in the presence of bile acids.

Conclusions: The results of this study provide a solid foundation for further research directed at the improvement of topical formulations using bile acids as penetration-enhancing excipients, as well as the therapeutic efficacy of clindamycin hydrochloride.