Plaster used as therapeutic system for the administration of active substances to the skin which exhibits a graduated active substance release, process for the production of the plaster and the use thereof

A plaster for the controlled release of active substance to the skin comprising

• a) a backing layer which is spaced from the skin, the backing layer comprising at least one material selected from the group consisting of polyethylene, polypropylene, polyester, polyamide, metal foil optionally coated with a polymeric substrate, textile fabric and polymer foil vapourized with metal,
• b) a matrix containing active substance in a first concentration, in use intended to contact the skin, the matrix comprising at least one polymeric material selected from the group consisting of rubber, a synthetic homo-, co- or block copolymer, a poly(meth)acrylate or copolymer thereof, a polyurethane, a silicone, polyvinylpyrrolidone, ethyl cellulose, hydroxypropylcellulose, hydroxypropylmethylcellulosephthalate, polyvinyl alcohol or a copolymer thereof with vinyl laurate or maleic acid, vinyl acetate or a copolymer thereof with vinyl laurate or maleic acid, a polyvinyl ether, butyl rubber and polycaprolactam,
• c) a deposit containing active substance in a higher concentration than said first concentration, in use intended to be spaced from the skin, said deposit contacting the matrix of lower concentration, the deposit comprising a single or multiple layer inserted between a back side matrix layer and a matrix layer on the skin side, when multiple layers are present their thickness ratio falling in the range of 1:1 to 1:20,
• d) and adhesive for adhering the lower concentration matrix to the skin,
• the dimension and position of the active substance deposit in contact with the matrix being chosen in such manner that, at least in one direction, the space between deposit and a matrix edge, which contacts the releasing surface, is larger than the diffusion path from the deposit into the matrix during the course of application of at least one active substance.