ignorance and confusion about the biological and psychological mechanisms of pain management and addiction (Bruera et al., 1987; WHO, 1990; Nestler et al., 1993; Von Roenn et al., 1993; Portenoy et al., 1994; Buchan and Tolle, 1995; Joranson, 1995a; Portenoy, 1996). Research indicates that addiction in patients appropriately receiving opioids for pain is very small, ranging from roughly 1 in 1,000 to less than 1 in 10,000 (Porter and Jick, 1980; Angell, 1982; Jaffe, 1985; Rinaldi et al., 1988; Portenoy and Payne, 1992; Portenoy, 1996).
The committee concluded that drug tolerance and physical dependence should be more uniformly and clearly distinguished from addiction. Tolerance occurs when a constant dose of a drug produces declining effects or when a higher dose is needed to maintain an effect. Physical dependence on opioids is characterized by a withdrawal effect following discontinuation of a drug. Such dependence is a common effect in chronic pain management, but it is not restricted to opioids. Other agents such as beta-blockers, caffeine, and corticosteroids also produce physical dependence. Further, clinical evidence suggests that patients receiving opioids can be easily withdrawn from them in favor of an alternative, effective pain control mechanism if that is clinically indicated. Typical practice is to reduce the dose by fractions, stopping administration of opioids altogether after a week or so (Doyle et al., 1993). This practice may not be relevant, however, for dying patients.
Neither physical dependence nor tolerance should be equated with addiction or substance abuse. Portenoy and Kanner (1996) proposed that "addiction is a psychological and behavioral syndrome characterized by (1) the loss of control over drug use, (2) compulsive drug use, and (3) continued use despite harm" (p. 257). This is consistent with a definition proposed by the American Medical Association: "the compulsive use of a substance resulting in physical, psychological, or social harm to the user and continued use despite that harm" (Rinaldi et al., 1988, p. 556). The federal Controlled Substances Act defines an addict as someone who habitually uses an opioid in ways that endanger public health or safety (AHCPR, 1994a).
Unfortunately, the general term substance dependence is often used as a synonym for addiction, perhaps because the latter is more stigmatizing. For example, the American Psychiatric Association sets out criteria for dependence rather than addiction in its Diagnostic and Statistical Manual of Mental Disorders (4th ed., 1995). Despite a disclaimer that the scheme focuses on "maladaptive" substance use, the discussion of substance dependence may nonetheless mislead (p. 181). A later disclaimer about distinguishing legitimate medical purposes from opioid dependence is not specific, given that, as described below, many seem to be confused about what is legitimate. The committee is particularly concerned about misinterpreta-