Under Siege: The Brain on Opiates

Many of the terms used in the addiction field today were developed originally based on the opiates, one of the oldest and best characterized classes of abused drugs. Tolerance describes the need for an increasing dose of opiate to achieve the same effect; this term was based originally on the tolerance that develops to many of the acute behavioral actions of opiates (e.g., analgesia, autonomic inhibition, and “high”). Dependence describes an altered physiological state caused by repeated opiate exposure such that cessation of drug administration leads to a withdrawal syndrome characterized by serious physiological disturbances. This term was used originally to describe physical opiate dependence as characterized by classical opiate withdrawal (i.e., “cold turkey”). More recently, it has become clear that opiates also result in a psychological form of dependence, which results in emotional or motivational symptoms upon drug withdrawal. This latter form of dependence is probably the strongest determinant of opiate addiction, which can be defined as compulsive drug craving and administration despite horrendous adverse consequences.