Development and in vitro evaluation of furosemide transdermal formulations using experimental design techniques.

The in vitro skin permeation of furosemide, a commonly used loop diuretic, through human epidermis, as a preliminary step towards the development of a transdermal therapeutic system, was examined. A screening study was carried out, in order to estimate the effects of the type, the concentration of enhancer and the concentration of gelling agent on the cumulative amount of furosemide permeated through human epidermis, using a 3(3) factorial design. The type and the concentration of enhancer were further evaluated as they were found to affect significantly furosemide permeation. In order to further increase the amount of the drug permeated, the combination of two enhancers, Azone and oleyl alcohol, at three concentration levels was employed, using an optimization technique. The results indicated that higher amounts of furosemide permeated were observed when Azone was used at 5.0-6.5% (v/v) and oleyl alcohol at 7.5-9% (v/v), in the gels used. These formulations seem to be suitable for possible transdermal delivery of furosemide for pediatric use.