In vitro transdermal permeation of nifedipine from thickened microemulsions.

The in vitro transdermal absorption of nifedipine from microemulsions was studied using the skin of the hairless mouse as membrane. Two microemulsions (N.1 and N.2) were prepared and thickened; they contained respectively 1.8% and 2.0% of nifedipine in solution. The fluxes of the drug from the microemulsions were 7.8 micrograms/h/cm2 from N.1 and 18.6 micrograms/h/cm2 from N.2. Two reference gels were prepared to examine whether the components of the microemulsion could behave as enhancer: their fluxes were very low, below 0.5 microgram/h/cm2. Nifedipine dissolved in microemulsion and protected from light showed no degradation for up to six months.