Microemulsion formulation design and evaluation for hydrophobic compound: Catechin topical application

Objective: The aim of the present study was to design nanocarriers for the topical application of rivastigmine. Methods: The effect of cosurfactants, hydrophilic gel and loading amount on the permeability of rivastigmine through rat skin was evaluated. Skin irritation tests and stability tests were performed to evaluate the utility of tested formulations. Results: The results showed that the microemulsion formation and characteristics of drug-loaded formulations were related to many parameters of the components. When using microemulsion systems as a vehicle, the permeation rate remarkably increased about 13.2~24.3-fold and the lag time was significantly shortened from 24 h to 4.7 h. Formulations containing a cosurfactant of Diethylene Glycol Monobutyl Ether (DEGBE) showed higher enhancement effect, while increasing the loading dose from 0.5% to 5% further increased the flux about 2.1-fold and shortened the lag time. Conclusion: The drug-loaded experimental formulation did not cause skin irritation and had good stability at 20ºC and 40ºC storage for at least 3 months. The result showed that gel-based microemulsion formulation could be a promising approach for topical administration.

Sebaceous gland tumors and other tumors exhibiting sebaceous differentiation have been described in humans (1,2,3). Tumors of the sebaceous gland can be induced in rats and mice following topical application of carcinogens (4), but spontaneous mixed tumors of basal cell origin rarely occur in mice.