Background: A new dermatopharmacokinetic (DPK) approach has been proposed for bioequivalence determination of topical drug products by comparing the drug content kinetics in stratum corneum.
Objective: We sought to establish any correlation between clinical safety/efficacy and DPK approach in bioequivalence determination of tretinoin gel 0.025%.
Methods: Tretinoin and isotretinoin were quantified in human volar forearm stratum corneum as a function of time with 3 tretinoin gel 0.025% products in 49 patients. Stratum corneum layers were harvested using multiple adhesive disks, which were subsequently extracted and quantified for both isomers by high-performance liquid chromatography.
Results: Products with similar composition and therapeutic equivalence were found bioequivalent, and products with different composition and clinical profiles were found bioinequivalent by DPK methodology.
Conclusions: There is a direct correlation between DPK parameters in healthy patients and clinical safety/efficacy of tretinoin gel products in patients with acne. Data support the use of DPK parameters and methodology in the bioequivalence assessment of topical tretinoin gel products.