Effect of oil phase composition on the skin permeation of felodipine from o/w microemulsions

Oil/water microemulsions containing benzyl alcohol or different ratios of benzyl alcohol and isopropyl myristate as oil phase were prepared and used as vehicles for the transdermal absorption of felodipine. Skin permeation from the microemulsions was compared with that from a drug suspension in an apparent external phase of a microemulsion and with an aqueous drug suspension. The highest flux was from the microemulsion with the highest solubility of felodipine, while the permeation rate decreased over time from the suspension in the apparent external phase. The flux from the aqueous suspension was 10-50 times lower than that from the microemulsions. These results indicate that microemulsions containing benzyl alcohol may be interesting vehicles for transdermal administration of felodipine.