Dibutyl Phthalate

Felodipine is an effective calcium channel blocker, mainly used in the treatment of hypertension and angina pectoris.  To overcome the low oral bioavailability of felodipine, the present work was designed to develop transdermal therapeutic system for felodipine using the polymer blend of eudragit RL 100 (ERL) / RS 100 (ERS) by solvent casting method. Dibutyl phthalate (DBP) and oleic acid (OA) were used as plasticizer and permeation enhancer respectively. Incorporation of DBP improved the flexibility, folding endurance and handling properties of the films. Increasing the concentration of ERL, and the presence of plasticizer were found to increase the in vitro drug release of the films.  The patches were also evaluated for ex vivo skin permeation using human cadaver skin. The presence of OA produced significant increase in the flux and permeability constant. The formulation with ERL: ERS ratio 4:1, 5% w/w OA as permeation enhancer and 20% w/w DBP as plasticizer showed the best results which exhibited the cumulative percentage of drug release of 75.73 ± 2.179 % and the cumulative amount of drug permeation across skin of 4321 ± 11.533 µg/cm2 in 24 hrs. Drug-excipient interaction studies were carried out using DSC and IR technique; films indicated no chemical interaction between drug and excipients. The results of the skin irritation studies showed no noticeable irritancy on rabbit skin indicating the skin compatibility of the drug as well as polymer.  An attempt was made to develop the complete transdermal system of the drug by using backing membrane and release liner.