Passive and Iontophoretic Delivery of Sildenafil Through the Skin
Sibel İLBASMIŞ TAMER*, Tuncer DEĞİM*^,o
* Gazi University, Faculty of Pharmacy, Department of Pharmaceutical Technology, Etiler, Ankara, Turkey

^oCorresponding Author

Summary

Sildenafil is a novel and recently approved drug used for the treatment of erectile dysfunction. Some concerns have arisen in the high-risk elderly related with sildenafil treatment, and there are published reports considering the possible negative effects of sildenafil and some suspicious sudden deaths. In such cases, the treatment needs to be stopped immediately; however, after oral administration, further sildenafil absorption cannot be stopped. One of the new approaches may be the use of iontophoresis.
There is no data available for sildenafil and its skin permeability; therefore, this study was aimed to determine sildenafil permeability through human skin.
Passive penetration properties of sildenafil were investigated through dialysis membrane, polydimethylsiloxane (PDMS)
membrane, excised rabbit skin, and human skin using Franz type diffusion cells. The permeability coefficients were determined in the following order: dialysis membrane> PDMS membrane> rabbit skin> human skin (log k values: -1.135>-2.694>-2.982>-2.995 cm/h, respectively).
A gel formulation of sildenafil was also developed and applied to dorsal rabbit skin. Blood sildenafil concentrations after passive diffusion, iontophoretic delivery and oral sildenafil administration were analyzed. Iontophoresis was found to be a very useful technique and method to increase sildenafil penetration through the skin.

Key Words :
Iontophoresis, sildenafil, anodal delivery, skin permeability.