Transdermal drug delivery system

PCT No. PCT/FI95/00358 Sec. 371 Date Jan. 7, 1997 Sec. 102(e) Date Jan. 7, 1997 PCT Filed Jun. 20, 1995 PCT Pub. No. WO96/01626 PCT Pub. Date Jan. 25, 1996A controlled release transdermal system for the delivery of at least one therapeutic agent comprises: a reservoir comprising (a) the therapeutic agent in ionized form and (b) a pH adjusting agent which upon uptake of water is converted to a buffer solution and (c) a cyclized polysaccharide selected from a group consisting of cyclodextrin, cyclodextrin derivative and cyclodextrin polymer, the cyclized polysaccharide being capable of improving the solubility of the therapeutic agent in the buffer solution by forming an inclusion complex with the therapeutic agent; and a reservoir wall comprising a polymer being substantially impermeable to the ionized form or to the inclusion complex form of the therapeutic agent but permeable to water and to the unionized form of the therapeutic agent. The system allows the release of a therapeutic agent which may be a weak acid or base in a manner which shows less variation between patients than previous systems.