A oral pharmaceutical composition for controlled release of an opioid from a pharmaceutical composition is described that comprises (i) an erodible matrix composition comprising a mixture of (a) a polymer or a mixture of polymers (b) an opioid, and optionally, (c) one or more pharmaceutically acceptable excipients; and (ii) a single, substantially insoluble in and impermeable coating having two openings exposing at least one surface of the matrix, and comprising one or more polymers. The composition exhibits controlled release of the opioid by erosion of the matrix and exhibits a zero order release profile wherein about 75% w/w of the opioid is released from the composition within 4-10 hours when tested in a dissolution test as described herein.