GB2290964A — Transdermal drug delivery system

USPTO Abstract

A controlled release transdermal system for the delivery of at least one therapeutic agent comprises: a reservoir comprising (a) the therapeutic agent (eg. weak acid or base) in ionized form (b) a pH adjusting agent which upon uptake of water is converted to a buffer solution and (c) a cyclized polysaccharide eg. cyclodextrin, cyclodextrin derivative or cyclodextrin polymer, 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 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. Water from skim penetrates the reservoir causing (b) to form a buffer solution; the change in pH causes the unionized form to form which permeates the reservoir wall. Upon partitioning of the unionized form to the reservoir wall, more therapeutic agent is released from the cyclized polysaccharide complex.