Transdermal delivery of hormones with low concentration of penetration enhancers

A composition for transdermal delivery comprising a drug-containing layer wherein the drug-containing layer comprises Gestodene or an ester thereof and at least one pharmaceutically acceptable carrier which comprises one or more polyisobutylene polymer(s), wherein the drug-containing layer contains 25% to 99% by weight of the polyisobutylene polymer(s), wherein the drug-containing layer has a solubility for said Gestodene or an ester thereof of no more than 3% by weight of the drug-containing layer and the Gestodene or an ester thereof is completely dissolved in the layer, wherein the Gestodene or an ester thereof is in an amount ranging between 0.5 and 3% by weight of the drug-containing layer, wherein the drug-containing layer comprises less than 1.0% by weight of a skin penetration or permeation enhancer, wherein the drug-containing layer further comprises a tackifier selected from the group consisting of hydrocarbon resins, rosin resins and terpene resins, and wherein the one or more polyisobutylene polymer(s) include at least one polyisobutylene polymer with a high molecular weight of about 500,000 to 2,000,000 Da and at least one polyisobutylene polymer with a low molecular weight of about 20,000 to 100,000 Da.