Patent ID: 8252331

Claim:
An osmotic device having a unitary core surrounded by a semipermeable membrane having at least one passageway there through, wherein: a) the unitary core comprises a mixture of amantadine salt, osmotic salt, and at least one other pharmaceutically acceptable excipient, wherein the amantadine salt is amantadine hydrochloride and the osmotic salt is sodium chloride, and the weight ratio of amantadine salt to osmotic salt ranges from 2:1 to 30:1; b) the osmotic salt is not coated with a release rate controlling coating; c) the permeability of the semipermeable membrane is adapted to cooperate with the osmotic salt to control the release profile of amantadine salt from the osmotic device; d) the amantadine salt and osmotic salt have an ion in common; e) amantadine salt is released through the one or more passageways according to a sigmoidal controlled release profile, optionally wherein release of amantadine salt is delayed for a period of time, when the osmotic device is exposed to an aqueous environment of use; and f) the semipermeable membrane comprises a cellulose acetate grade 1 and a cellulose acetate grade 2, wherein the weight ratio of a cellulose acetate of high viscosity to the total amount of cellulose acetates ranges from 0:1 to 1:1, the cellulose acetates grade 1 has 7-10% by wt of hydroxyl groups, 30-36% by wt. of acetyl groups and a viscosity of 200-280 seconds, the cellulose acetate grade 2 has 3-5% by weight of hydroxyl groups, 37-43% by wt. of acetyl groups and a viscosity of 6.0-45.0 seconds, the unitary core comprises less than 6% of NaCl w/w based upon the weight of the uncoated core, and the semipermeable membrane comprises more than 25% w/w of cellulose acetate grade 1 based upon the weight of the semipermeable membrane.