Solid dipersions included in poloxamer hydrogels have favorable rheological properties for topical application and enhance the in vivo antiinflammatory effect of ursolic acid

Abstract

Ursolic acid (UA) solid dispersions (SD) formulated into poloxamer-hydrogels were prepared for local treatment of skin inflammations. The hydrogel physico-chemical properties were evaluated, including rheology, in vitro drug permeation and cytotoxicity. The anti-inflammatory activity of the systems was investigated using the animal model of croton oil-induced ear edema. The formulations demonstrated a pseudoplastic behavior and elastic properties (G’ > G”). SDs in hydrogels demonstrated less resistance to flow, an increase in the sol-gel transition temperature and a decrease in G′ followed by an increase in G″ when compared to the hydrogel obtained only in NaCl solution. Bioadhesion and texture properties proved the formulations were suitable for topical application. Hydrogels controlled the diffusion process of the drug within the polymeric network, due to the higher viscosity of this systems. The permeability studies showed that the formulations composed of D-α-tocopheryl polyethylene glycol 1000 succinate provided greater UA diffusion through the skin. The anti-inflammatory effect of UA-SDs was significantly improved when formulated in poloxamer hydrogels, with the ability to inhibit 41.87% and 56.64% of edema when compared to the group of animals that did not receive treatment (negative control). These results indicate the advantages of UA-loaded SDs incorporated into hydrogel for topical treatment of inflammatory skin disorders.