Transdermal drug delivery systems are basically patches or films applied to an intact skin to deliver bioactive substances at controlled rate to the blood through the skin. The aim of this study is to investigate the physico-chemical, mechanical and permeation properties of diazepam transdermal delivery patches. Diazepam transdermal films were prepared with blends of hydroxypropyl methylcellulose (Hypromellose, HPMC) and extracted cassava starch using solvent casting technique. Different transdermal films were also produced using polyvinyl alcohol (PVA) as film- former. The patches were evaluated for stability, thickness, folding endurance, moisture uptake and loss, elongation break, swelling index and ex vivo skin permeation studies. The patches were stable, with satisfactory dimensions and PVA batches showing the highest folding endurance (339-404 cycles) whereas HPMC-cassava starch hybrids showed higher moisture uptake and loss. Furthermore, the PVA patches were less elastic. Transdermal patches prepared with HPMC and cassava starch at 4:1 ratio (HC4) showed the highest diazepam permeation, flux (83.3 µg/cm2 h) and permeation constant (0.0022cm.h-1) (p<0.05). Transdermal patches prepared with these polymers can be effectively used to deliver diazepam drug.

This review covers the basic principles of chemistry used in molecular modeling as they apply to medicinal chemistry. This is necessitated from the fact that the use of computers in drug design and development has become a common practice.