The use of opioids for the treatment of chronic nonmalignant pain was mired in controversy for many years (Portenoy, 1996). It was once thought that long-term opioid use led to a downhill spiral associated with a loss of functional capacity and depressed mood (Ciccone et al., 2000). We now know that this is not the case. Other evidence also indicates that a subpopulation of patients with chronic pain can achieve sustained partial analgesia from opioid therapy without the occurrence of intolerable side effects (Savage, 1999). Impairment of daily activity, psychomotor speed, and sustained attention and mood have also been reported to improve with long-term opioid treatment for this population (Haythornthwaite et al., 1998). A meta-analysis of the opioid treatment literature has also indicated that, in general, patients with chronic pain will respond to long-term opioid therapy (Graven et al., 1999). Thus, at the present time, there is little controversy over whether opioids can be used for the treatment of pain when other options have been exhausted.
Although it appears that there has been a literature consensus reached on the need for chronic opioid treatment for patients with chronic pain if other treatments fail, there is a subpopulation within this group that is problematic. These are the patients who may demonstrate addiction to opioids.
Addiction in Patients With Chronic Pain
In 2001, the American Academy of Pain Medicine, the American Pain Society and the American Society for Addiction Medicine approved the following definition for addiction (Savage et al., 2001):
Addiction is a primary, chronic, neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over drug use, compulsive use, continued use despite harm, and craving.
The DSM criteria for drug dependence do not really address this concept of addiction. For example, of seven criteria (of which three are required to fulfill this diagnosis), one relates to tolerance and one relates to withdrawal. If patients with chronic pain are on significant opioids, they are invariably tolerant to opioids and manifest withdrawal when removed from them. Thus, these two criteria could lead to over-inclusiveness for this diagnosis. In addition, the criteria of "the substance is often taken in larger amounts å than intended" and "persistent desire å to cut down" can simply relate to the need to control pain. Thus, four out of seven criteria may lead to over-inclusiveness in the application of this diagnosis to the patient with chronic pain.
Fishbain et al. (1992) addressed the DSM criteria. Through a review process, my colleagues and I attempted to delineate what were the reported prevalence percentages for addiction in patients with chronic pain. We reported that different authors utilized different definitions and criteria (Fishbain et al., 1992). Overall, the prevalent percentages for drug abuse/dependence/addiction for patients with chronic pain was in the range of 3.2% to 18.9%. We cautioned that these results did not tap the concept of addiction and that the prevalence of addiction was likely at the lower end of this range.
There have been a significant number of other studies that have directly or indirectly explored this issue. Hoffmann et al. (1995) found an addiction rate of 23.4%, Chabal et al. (1997) found an addiction rate of 34% and Kouyanou et al. (1997) found a rate of 12%. There has also been one report relating to chronic pain populations at a U.S. Veterans' Affairs (VA) facility and a primary care setting. In this study, Reid et al. (2002) found that prescription opioid abusive behavior was recorded for 24% of the VA patients and 31% of the primary care patients. As "opioid abusive behavior" does not necessarily translate into addiction, one does not know how to interpret these results.
In addition, there have been two studies utilizing urine toxicologies for inpatients with chronic pain using illicit drugs. In the first study, Fishbain et al. (1999) reported that 8.4% of the patients had illicit drugs in their urine, while Rafii et al. (1990) reported a rate of 12.5%. Since illicit drug use has a high correlation with a predisposition to addiction in patients with chronic pain (Sees and Clark, 1993), these figures probably represent the lower end in the range for prevalence of addiction. Although the above studies attempted to develop prevalence percentages for substance use disorders, none of them utilized control groups. A study by Brown et al. (1996) compared rates for substance use among patients with chronic pain attending a family medicine clinic to patients attending for other reasons. There was no statistical difference in prevalence between the two groups. Thus, it is possible that the prevalence of drug addiction in patients with chronic pain is no greater than that in other patients. This statement is even more relevant if one understands that the aforementioned drug addiction data were reported from tertiary facilities where patients with chronic pain who have more significant problems are treated. While these data indicate that the prevalence of addiction may not be too much different from the general population, they are limited by the problems with the definition and the diagnosis of addiction.