11 DESCRIPTION The Estradiol Transdermal System (estradiol transdermal system), is designed to release estradiol continuously upon application to intact skin. Six (6.5, 9.375, 12.5, 15, 18.75 and 25 cm 2 ) systems are available to provide nominal in vivo delivery of 0.025, 0.0375, 0.05, 0.06, 0.075 or 0.1 mg respectively of estradiol per day. The period of use is 7 days. Each system has a contact surface area of either 6.5, 9.375, 12.5, 15, 18.75 or 25 cm 2 , and contains 2, 2.85, 3.8, 4.55, 5.7 or 7.6 mg of estradiol USP respectively. The composition of the systems per unit area is identical. Estradiol USP is a white, crystalline powder, chemically described as estra-1,3,5(10)-triene-3, 17β-diol. It has an empirical formula of C 18 H 24 O 2 and molecular weight of 272.38. The structural formula is: The Estradiol Transdermal System transdermal system comprises three layers. Proceeding from the visible surface toward the surface attached to the skin, these layers are: A translucent polyethylene film. An acrylate adhesive matrix containing estradiol USP. A protective liner of siliconized or fluoropolymer-coated polyester film is attached to the adhesive surface and must be removed before the system can be used. The active component of the transdermal system is estradiol. The remaining components of the transdermal system (acrylate copolymer adhesive, fatty acid esters, and polyethylene backing) are pharmacologically inactive. Chemical Structure Patch Diagram