Development of a film-forming oleogel with increased substantivity for the treatment of psoriasis.

The aim of this work was the development of a film-forming formulation (FFF) for the topical treatment of psoriasis that shows an increased substantivity compared to conventional semi-solid dosage forms. The developed formulation is an oleogel. It is based on a combination of castor oil and medium chain triglycerides, and the oil-soluble film former MP-30 (Croda GmbH, Nettetal, Germany), a polyamide that upon mixing with a polar oil entraps the oil und thus substantially increases the viscosity of the formulation up to a semisolid state. Betamethasone dipropionate (BDP) and calcipotriole (CA) were used as active pharmaceutical ingredients (APIs). Oleogels of different compositions were evaluated regarding substantivity, rheological properties, ex-vivo penetration into the skin and ex-vivo permeation through the skin. Marketed products were used as controls. It was found that the amount of betamethasone dipropionate penetrating and permeating into and through the skin from the film-forming formulation is at an intermediate value compared to the marketed products. The substantivity of the developed formulation is described by an amount of 57.7 % formulation that remains on the skin surface and is thus significantly higher compared to the marketed products. In the film forming formulation, the proportion of API penetrating the skin remains the same when the skin repetitively brought in contact with a piece of textile during the penetration experiment. In contrast with the in-market formulations tested, this proportion was reduced by up to 97 %. As a result, the developed formulations can lead to an increased patient compliance.