Enhancement of transdermal penetration of dapiprazole through hairless mouse skin

The in vitro permeation rate of dapiprazole base (DAP-B) through hairless mouse skin was investigated, as a preliminary step towards the development of a transdermal therapeutic system. The study involved the evaluation of the permeability coefficient of the drug applied to the skin in a series of liquid and semisolid vehicles, both in the absence and in the presence of different penetration enhancers. In liquid vehicles the permeability coefficient of DAP-B was significantly promoted (up to 73 times) by some terpenes (l-limonene, alpha-bisabolol, terpinolene) and by a mixture of unsaturated fatty acids. Similar effects were noted in semisolid vehicles, although the permeability coefficients were lower. Iontophoretic experiments on DAP-B in physiological saline solution, at constant current densities in the range of 0.05 - 0.5 mA/cm(2), produced up to 115-fold permeability increases relative to passive diffusion. The present results, even if needing further corroboration by tests on human skin, evidenced the activity of some molecules as skin permeation enhancers for DAP-B, and confirmed the synergy between propylene glycol and the enhancers, already reported in the literature. The possibility of promoting DAP-B transport through the skin by iontophoresis was also established.