Comparison of rheological properties, follicular penetration, drug release, and permeation behavior of a novel topical drug delivery system and a conventional cream.

A novel adapalene-loaded solid lipid microparticle (SLMA) dispersion as a topical drug delivery system (TDDS) for follicular penetration has been introduced. The objective of the present study was to investigate the rheological properties, the follicular penetration with differential tape stripping on porcine ear skin, the drug release in sebum and stratum corneum (SC) lipid mixtures, and the permeation behavior across human SC in comparison with a commercially available cream as standard. Physicochemical characterization reveals that adapalene is homogeneously distributed within the SLMA dispersion and chemically stable for at least 24 weeks. The SLMA dispersion shows a lower complex viscosity at 20 °C and a higher one at 32 °C than the cream, while the phase angle of the dispersion is always larger at both temperatures. Both formulations feature an equivalent potential for follicular penetration and deposition. However, the superiority of the SLMA dispersion is based on the preferential drug release in sebum while there is no or just a slight release in SC lipids and no permeation for both formulations. Due to the similarity of the glyceride matrix of the SLMA to sebum components, a targeted drug delivery into sebum and thereby an increased follicular penetration may be facilitated.