Abstract: A composition for controlled release of an opioid from a pharmaceutical composition, the method comprises controlling the release of at least one opioid into an aqueous medium by erosion of at least one surface of a pharmaceutical composition comprising I) a matrix composition comprising a) polymer or a mixture of polymers, b) an opioid and, optionally, c) one or more pharmaceutically acceptable excipients, and (i) a coating. The matrix composition has a conus-like shape so the surface area exposed to the aqueous medium increases at least during initial erosion of the matrix composition, and the dissolution of the opioid-when tested in a Dissolution Test as described herein with or without application of sinkers-results in a zero order release of at least 80% of the opioid contained in the composition. Such compositions are especially suitable for controlled release of an opioid to obtain a delayed pead concentration and a prolonged therapeutically effective plasma concentration upon oral administration.