Alkyl polyglucoside-based adapalene-loaded microemulsions for targeted dermal delivery: Structure, stability and comparative biopharmaceutical characterization with a conventional dosage form

Abstract

Aiming to develop biocompatible microemulsions based on natural alkyl polyglucoside surfactant as prospective carriers for improved dermal delivery of adapalene, phase behavior and microstructure of pseudo-ternary oil/decyl glucoside/propylene glycol/water systems were evaluated. The chosen inverted bicontinuous formulations did not change their microstructure upon drug incorporation and remained stable during 1-year period. Preliminary in vivo assessment of skin performances suggested satisfying safety profiles of placebo microemulsions, in spite of considerable changes in skin hydration and barrier function. Interestingly, despite lower in vitro drug release, the amount of adapalene penetrated into porcine skin under infinite dosing regime was higher from microemulsions than from commercial drug product, reaching dermal retention enhancement ratio of 5.9. However, by changing experimental conditions to the more realistic in-use situation, the amount of adapalene extracted from the stratum corneum was comparable for microemulsions and marketed product. Similarly, the drug deposition in hair follicles was slightly pronounced with novel microemulsion vehicles (183.30 ± 156.32 ng/cm2 and 167.39 ± 108.96 ng/cm2 vs. 157.00 ± 114.91 ng/cm2), highlighting the importance of proper selection of experimental conditions when assessing trans(dermal) drug delivery. Consequently, our results suggest that alkyl polyglucoside based microemulsions are promising vehicles worth exploring further for targeted intraderdermal delivery of adapalene in acne treatment.