An opioid-antagonist oral dosage form which does not release a therapeutically effective amount of the opioid antagonist when the oral dosage form is orally administered to a human being, but whereby a physical alteration of the oral dosage form results in a release of the therapeutically effective amount of the opioid antagonist. An embodiment of the oral dosage form includes an opioid-antagonist layer coated onto a biologically inert pellet, and a non-releasing membrane coated onto the opioid-antagonist layer. Optionally, the oral dosage form can also include an opioid agonist, such that a method of preventing the abuse of an oral dosage form of an opioid agonist is provided by forming the oral dosage form including an opioid agonist and an opioid antagonist.