Abstract

The invention relates to transdermal drug patches for the controlled release of drugs to the human skin, comprising(a) an impermeable backing or covering layer,(b) a reservoir layer adjacent to, and in close contact with said backing or covering layer, said reservoir layer comprising a polymer matrix composed of a rubber and an adhesive resin material wherein said therapeutically active agent or agents are wholly or partially soluble and which is permeable to said agent or agents,(c) an adhesive layer adjacent to, and in close contact with, said reservoir layer and permeable to said therapeutically active agent or agents, and(d) a protective layer covering and adhearing to said adhesive layer and removeable therefrom for the use of said transdermal drug patch,the improvement wherein said drug or drugs in the rubber and adhesive resin material of the reservoir layer are present together with a polymer capable of swelling in water and insoluble in the rubber and adhesive resin material of the reservoir layer, the quantity of said polymer being between 3 and 30% by weight of the rubber and adhesive resin mixture.By the incorporation of this particular water-swellable polymer material in the rubber/adhesive resin mixture together with the drug which polymer material is insoluble in the matrix, in a particular proportion calculated to the weight of the rubber and adhesive resin material in particular the drug release from the patch to the skin is increased to twice or even more is achieved.