A Parmaceutical Study on Felodipine(Preparation and evaluation of Felodipine Therapeutic Transdermal system) Ahmed Abd El-Bary, Mohamed M. Nafady, Mahmoud E. Nasr Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Cairo University,Egypt.

Aim of work Transdermal therapeutic systems were prepared in order to control the permeation of the drug through membranes and develop a transdermal path to deliver felodipine at a controlled rate thus bypassing the hepatic metabolism of the drug and increasing its bioavailability.

The in-vivo evaluation of certain selected formula of felodipine therapeutic transdermal system(microemulsion composed of benzyl alcohol : water : transcutol : taurodeoxycholate : tween20 in ratios of 17.3:47.7:15.9:1.0:18.1 respectively ) in rabbits were carried out.

Conclusion 1-Permeation of felodipine through EVA membranes increases significanly when the membranes are stored for three days in contact with the drug solution. 2-The amount of felodipine permeated through membranes with different levels of VA, copolymer increases as the weight fraction of the copolymer increases, in the rank order 28%>19%>9% VA content.

3-The permeation of felodipine from its microemulsion system IV showed the highest amount of drug permeation compared to other microemulsion systems. 4-The effect of d-limonene as a permeation enhancer on the permeation of felodipine through new born rabbit skin resulted in nearly about five fold increase in the amount of felodipine permeated through the skin.

5-Kinetic analysis of the permeation data revealed that felodipine permeation through EVA membranes follows zero order diffusion and first order mechanisms.

6-From bioavailability study ; felodipine transdermal patches controlled the permeation of the drug for an extended period of time, resulting in a significant increased bioavailability as reflected by the increase in the area under plasma concentration time curve, it can be predicted that the required minimum effective concentration could be achieved in humans in spite of the greater barrier properties of human skin compared to rabbit skin.

7-An approximation of the usefulness of the use of transdermal administration of felodipine in humans can be determined by estimating the application area of the drug delivery system or the patch used to deliver the drug.

Amount of felodipine permeated(mg) after the following periods of time(min) MicroemulsionSystem I II III IV