The disclosure relates to a solid controlled release dosage form comprising: a core comprising a first portion of an opioid analgesic dispersed in a first matrix material comprising polyethylene oxide having an average molecular weight from about 300,000 to about 10,000,000； and a shell encasing the core and comprising a second portion of the opioid analgesic dispersed in a second matrix material comprising polyethylene oxide having an average molecular weight from about 1,000,000 to about 10,000,000. The molecular weight of the polyethylene oxide in the first matrix material is lower than the molecular weight of the polyethylene oxide in the second matrix material. The amount of opioid analgesic released from the dosage form may be proportional within 20% to elapsed time from 8 to 24 hours, as measured by an in- vitro dissolution in a USP Apparatus 1 (basket) at 100 rpm in 900 ml simulated gastric fluid without enzymes (SGF) at 37 degrees C. The first and second matrix material may comprise polyethylene oxide and the opioid analgesic may be selected from codeine, hydrocodone, hydromorphone, morphine, oxycodone, oxymorphone or tramadol. The disclosure also relates to methods of producing the solid controlled release dosage form.
