Transdermal system exhibiting graduated drug release and its use for the local or systemic administration of active substances

A transdermal system for the controlled administration of an active substance to the skin, which exhibits a high initial dosage and a lower maintenance dosage and consists of:

• (A) a backing layer impermeable to the active substance and, in use, to be spaced from the skin,
• (B) a reservoir having two portions,
• (i) a first active substance portion adjacent the backing layer, and
• (ii) a second active substance portion having a predetermined releasing surface for the active material,
• (C) a pressure-sensitive adhesive for securing the second active substance reservoir portion to the skin, and
• (D) a membrane between the first and second active substance reservoir portions, the membrane being permeable to the active substance and including openings through which the active substance can pass, the surface area of said openings being smaller than the releasing surface area of the second reservoir portion, whereby the second reservoir portion initially releases its active material to the skin while the flow of active material from the first to the second reservoir portion is restricted by the membrane, so that there is an initial high rate of transfer of active material followed by a lower controlled rate of transfer.