The invention combines two different subunits with different release profiles in novel sustained-release oral dosage forms. In particular, the oral dosage forms include a subunit that comprises an opioid analgesic and a sustained-release material, wherein the dissolution rate in-vitro of the subunit, when measured by the standard USP Drug Release test of U.S. Pharmacopeia XXVI (2003) <724>, is less than about 10% within about 6 hours and at least about 60% within about 24 hours less than about 10% within about 8 hours and at least about 60% within about 24 hours or less than about 10% within about 12 hours and at least about 60% within about 24 hours the dosage form providing a duration of therapeutic effect of about 24 hours.
