| abstract |
A pharmaceutical composition for controlled release of an active substance. The active substance is released into an aqueous medium by erosion of at least one surface of the composition. The composition comprises i) a matrix comprising a) polymer or a mixture of polymers, b) an active substance and, optionally, c) one or more pharmaceutically acceptable excipients, and ii) a coating. Zero order release is desirable. The matrix typically comprises PEO and the active substance is typically an opioid such as morphine or a glucuronide thereof. The coating comprises a first cellulose derivative which is substantially insoluble in the aqueous medium and at least one of a) a second cellulose derivative which is soluble or dispersible in water, b) a plasticizer, and, d) a filler. |