Transdermal delivery system utilizing one way membranes

Abstract

A system for transdermally delivering a hydrophobic alkanol soluble active agent to the skin at a constant rate utilizing a lower alkanol penetration enhancer. The system comprises an overlying solvent reservoir containing a lower alkanol solvent and a drug compartment containing an active agent in aqueous alkanol. A one-way membrane is sandwiched between and divides the solvent reservoir from the drum compartment. The one-way membrane is permeable to the alkanol solvent and substantially impermeable to back flux of drug and water into the reservoir. An outer membrane permeable to the alkanol solvent and drug is attached to the outer surface of the drug compartment. Adhesive means is contained on the outer surface of this membrane for attaching the delivery system to the skin of a wearer. Alkanol from the reservoir permeates into the drug compartment and drug and alkanol pass through the outer membrane to the skin of the wearer for transdermal absorption. The rate of alkanol permeation from the reservoir to the drug compartment and from the drug compartment to the skin is substantially constant. The membrane is made up of an epoxidized silicone rubber to which is preferably laminated a layer of a dense hydrophobic copolymer of vinyl-terminated polydimethyl siloxane with methylhydro-dimethyl siloxane. If desired, to prevent any back flux of hydrophobic drugs, and additional layer of cellulose acetate may be sandwiched between the epoxidized silicone rubber and dense hydrophobic membrane.