Factors affecting percutaneous absorption

1) Drug concentration 2) The larger the area of application(larger TDDS), the more drug is absorbed 3 Aqueous solubility of a drug and Partition coefficient - Drugs penetrate the skin better in their un-ionized form - Nonpolar drugs penetrate lipid rich regions - Polar drugs favor transport between cells 4 Drugs with molecular weights of 100 to 800 and adequate lipid and aqueous solubility can permeate skin. The ideal molecular weight of a drug for transdermal drug delivery is believed to be 400 or less 5 Hydration of the skin generally favors percutaneous absorption. 6 Percutaneous absorption greater when thin horny layer 7 longer the medicated application contact - greater total absorption