Development and in vitro evaluation of diflucortolone valerateloaded topical microemulsion formulations

Topical corticosteroids are a group of drugs that are frequently used in the treatment of skin diseases that require anti-inflammatory and immunosuppressant effects. They alleviate inflammation by inhibiting vasodilation and increasing vascular permeability. They are frequently used in the treatment of skin diseases such as psoriasis, atopic dermatitis, eczema and lichen sclerosis. Topical corticosteroids are classified according to their potency. Accordingly, Diflucortolone valerate is in the group of potent corticosteroids. When designing a new formulation of this molecule, it should be considered that it is lipophilic and has poor water solubility. Diflucortolone valerate is available in conventional cream and ointment forms on the market. Topical drug administration is one of the most attractive drug administration routes. However, the skin constitutes an important barrier for drug absorption. The drug to be applied topically must first penetrate the stratum corneum layer. Understanding the parameters that affect the permeability of this barrier is very important for successful drug therapy through the skin. Factors affecting drug absorption from the skin can be summarized as the absorption parameters, the type of drug delivery system, the concentration of the drug and the site where the drug is administered. Microemulsions are optically isotropic and thermodynamically stable systems with droplet size generally in the 10-100 nm range. They are disperse systems consisting of oil, surfactant, co-surfactant and an aqueous phase. As drug carrier systems, microemulsions have properties such as thermodynamic stability, ease of formation, and improving the dissolution of molecules with lipophilic properties. In this thesis, diflucortolone valerate loaded microemulsions were developed and characterized. The stability of the microemulsions was followed for 3 months. In vitro release experiments were performed with optimized formulations. When compared with the conventional cream formulation, the release of drug from microemulsions was siginificantly higher. In conclusion, diflucortolone loaded microemulsions can be used as alternative drug delivery systems in topical corticosteroid applications. Keywords: Diflucortolone valerate, microemulsions, colloidal drug delivery systems, topical corticosteroids, topical drug delivery