Opioid formulations having extended controlled released

A solid controlled release oral dosage form, the dosage form consisting of a plurality of inert pharmaceutical beads coated with an analgesically effective amount of an opioid analgesic or a mixture of opioid analgesics or a salt thereof said inert pharmaceutical beads overcoated with a controlled-release coating, wherein the dissolution rate in-vitro of the dosage form, when measured by the USP Paddle Method of U.S. Pharmacopeia XXII (1990) at 100 rpm at 900 ml aqueous buffer at 1.6 and 7.2 pH and 37.degree. C. is from about 16.8% to about 42.5% (by wt) opioid released after 1 hour, from about 25% to about 65% (by wt) opioid released after 2 hours, from about 45% to about 85% (by wt) opioid released after 4 hours and greater than about 60% (by wt) opioid released after 8 hours, the in-vitro release rate being substantially independent of pH in that a difference at any given time between an amount of opioid released at one pH and an amount released at any other pH, when measured in-vitro using the USP Paddle Method of U.S. Pharmacopeia XXII (1990) at 100 rpm in 900 ml aqueous buffer, is no greater than 10%, the in-vitro release rate being chosen such that the peak plasma level of said opioid obtained in-vivo occurs from about 2 to about 8 hours after administration of the dosage form;

• said dosage form providing an extended duration of therapeutic effect of about 24 hours.