Development and validation of a simple chromatographic method for simultaneous determination of clindamycin phosphate and rifampicin in skin permeation studies

[Display omitted] •HPLC method for simultaneous determination of clindamycin and rifampicin in skin.•Method with an extreme capacity of drugs recovery from skin matrix.•The HPLC method complied with all international regulatory requirements.•The method acts as instrument for the development of new topical formulations. Rifampicin (RIF) and clindamycin phosphate (CDM) are the main drugs currently used in combination to treat severe infectious diseases in hair follicles. This work describes a simple, rapid and sensitive method for simultaneous analysis of RIF and CDM in the different skin layers using high performance liquid chromatography (HPLC). The efficient chromatographic separation of CDM and RIF was succeeded using a C18 column (150 mm x 4.6 mm, 5 μm) with gradient elution using a mobile phase composed of 0.01 M phosphoric acid and methanol at a flow rate of 1 mL min−1. Determinations were performed using UV–vis detector at 200 nm and 238 nm for CDM and RIF, respectively. The method was precise, accurate and linear (r2 > 0.999) with regression curve in the concentration range from 0.5 to 20.0 μg mL-1 and recovery rates from the skin layers higher than 85%. The retention times for CDM and RIF were approximately 7.4 and 12.2 min, respectively. The presence of skin components did not interfere with the analysis. The validated method was therefore appropriate for quantification of both CDM and RIF and thus may be feasible to be used in skin permeation studies.