This invention provides a polymeric diffusion matrix comprising glycerol, polyvinylalcohol, a water-soluble polymer having hydration sites which in combination with the remaining ingredients yields a matrix capable of sustained release of a drug dispersed therein, and water. The matrix may further include a drug for topical or transdermal application to a patient. The invention also provides a method of making the polymeric diffusion matrix and a drug delivery device incorporating the matrix. The matrix may be used in the form of a package, which comprises the matrix (14) embedded in a backing member (10) provided with a detachable cover layer (12). Before use, the cover layer is removed, and the backing member applied to the patient by means of a pressure-sensitive adhesive layer (26), so that the matrix (14) is held against the skin of the patient.
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