The present application relates to a transdermal drug delivery composition comprising (a) a copolymer comprising (i) one or more A monomers selected from the group consisting of alkyl acrylates containing 4 to 12 carbon atoms in the alkyl group and alkyl methacrylates containing 4 to 12 carbon atoms in the alkyl group； and (ii) one or more ethylenically unsaturated B monomers copolymerizable with the A monomer and containing a functional group selected from the group consisting of sulfonamide, urea, carbamate, carboxamide, hydroxy, amino, and cyano； and (b) about 8% to about 30% by weight fentanyl based on the total weight of the composition.
