Controlled Penetration of a Novel Dimeric Ceramide into and across the Stratum Corneum Using Microemulsions and Various Types of Semisolid Formulations.

Ceramides (CERs) are integral parts of the intercellular lipid lamellae of the stratum corneum (SC), which is responsible for the barrier function of the skin. Many skin diseases such as atopic dermatitis and psoriasis are associated with the depletion or disturbance of the level of CERs in the SC. Administration of an exogenous novel dimeric ceramide (dCER) deep into the SC may help to stabilize the SC barrier substantially and to treat some skin disease conditions. Consequently, with the help of the existing technology, it might be possible to formulate various pharmaceutical dosage forms that can facilitate penetration of dCER into the SC. Therefore, the penetration of dCER was studied using a high-performance liquid chromatography/atmospheric-pressure ionization/mass spectrometry method for the detection and quantification of exogenous dCER in the SC as well as other skin layers. Penetration studies were carried out in the Franz diffusion cell using excised human skin ex vivo. Penetration of dCER was studied with 3 model formulations: a colloidal formulation (microemulsion), a cream formulation with ethoxydiglycol as penetration enhancer and a nanoformulation. The highest concentrations of dCER in the different skin layers were found after application of the cream with penetration enhancer. Surprisingly, the lowest concentrations of dCER in the different skin layers were found after application of the microemulsion.