diacetylmorphine
n. the chemical name for heroin. A synthetic analog of morphine (produced by substituting acetyl groups for hydroxyl groups at two positions on the morphine molecule), it is, like morphine and codeine, a pure opioid agonist, activating receptors for endorphins and enkephalins (see endogenous opioid). Diacetylmorphine has a rapid onset of action and a duration of action similar to that of morphine; however, it is three times more potent than morphine. In Great Britain and Canada, it is used clinically in the management of severe pain—for example, in terminally ill patients—but it is not legally available in the United States due to concerns about its potential for abuse. Also called diamorphine. See opioid analgesic.