Nitroglycerin is 1,2,3-propanetriol, trinitrate, an organic nitrate whose structural formula is

and whose molecular weight is 227.09. The organic nitrates are vasodilators, active on both arteries and veins.

The Transderm-Nitro (nitroglycerin) transdermal system is a flat unit designed to provide continuous controlled release of nitroglycerin through intact skin.

The rate of release of nitroglycerin is linearly dependent upon the area of the applied system; each cm² of applied system delivers approximately 0.02 mg of nitroglycerin per hour. Thus, the 5-, 10-, 20-, and 30-cm² systems deliver approximately 0.1, 0.2, 0.4, and 0.6 mg of nitroglycerin per hour, respectively.

The remainder of the nitroglycerin in each system serves as a reservoir and is not delivered in normal use. After 12 hours, for example, each system has delivered 10% of its original content of nitroglycerin.

The Transderm-Nitro system comprises four layers as shown below. Proceeding from the visible surface towards the surface attached to the skin, these layers are: 1) a tan-colored backing layer (aluminized plastic) that is impermeable to nitroglycerin; 2) a drug reservoir containing nitroglycerin adsorbed on lactose, colloidal silicon dioxide, and silicone medical fluid; 3) an ethylene-vinyl acetate copolymer membrane that is permeable to nitroglycerin; and 4) a layer of hypoallergenic silicone adhesive. Prior to use, a protective peel strip is removed from the adhesive surface.

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