Opioid Overview

The important role opioids play in the treatment of pain, including non-malignant causes, is well supported (Savage 2003). However, an obstacle to effective use of opioids in pain treatment is the misunderstanding of the nature and risk of addiction when using opioids. The prevalence of drug abuse, dependence, or addiction in chronic pain patients has been stated to range from 3 to 19%. The concern of the medical community to not "fuel" this problem in chronic pain patients has led to less than optimal treatment of these patients. With these data, 81-97% of chronic pain patients were undertreated for fear of misuse or abuse of prescription medication.

Significant variation in the definitions and even diagnostic criteria of addiction is found within the medical, scientific, and political communities, as well as the general population. Such disparities result in misdiagnosis and undertreatment of addiction and pain syndromes. For the patient suffering from either one or even both conditions, could lead to a continued decrease in function, prolonged disability and pain, misuse of medications, and a decreased quality of life.

Historically, addiction-related terminology was confusing and ill-defined. This was most likely attributed to a poor understanding of the disease of addiction and its neurobiologic basis. Advances in addiction research have led to a greater understanding of the neurobio-logical basis of addiction, as well as the genetic and environmental influences that may effect its expression, and of course, the behavioral pathology that results in significant harm to the patient as well as any individuals affected by such behavior. With such a strong need for clarification of terminology, consensus definitions were established through collaboration of the American Academy of Pain Medicine, the American Pain Society, and the American Society of Addiction Medicine.

The defined addiction-related terminology is based on the following three points and is also summarized in Table 8.1:

1. Although some drugs produce pleasurable reward, critical determinants of addiction also rest with the user.

2. Addiction is a multidimensional disease with neurobiological and psychosocial dimensions.

3. Addiction is a phenomenon distinct from physical dependence and tolerance.

Historically, past definitions of addiction and dependence included references to tolerance and physical dependence as necessary elements of addiction. Although physical dependence and tolerance may occur in addiction, they do not necessarily have to be present. Moreover, physical dependence and/or tolerance may occur in the absence of addiction.

Table 8.1 Addiction-related terminology.

Tolerance A state of adaptation in which exposure to a drug induces changes that result in a diminution of one or more of the drug's effects over time Physical dependence A state of adaptation that is manifested by a drug class-specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood level of the drug, and/or administration of an antagonist Addiction A primary, chronic neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development or 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 clinical relevance is that misunderstanding the definitions of physical dependence, tolerance, and addiction can lead to overdiagnosis of addiction with the therapeutic use of opioids and other drugs, as well as underrecognition of addiction to substances that do not result in demonstrable physical dependence.

For example, beta-blockers as well as clonidine, an a-2 agonist, used to control hypertension, can cause profound rebound hypertension upon abrupt cessation of the drugs, reflecting physical dependence, although no behavioral compulsions or psychological aberrations result from discontinuation of the drug. Intranasal phenylephrine (AfrinĀ®) can cause significant physical dependence, even after short-term use, as severe rebound nasal congestion can occur with continuous use of intranasal phenylephrine for as little as 3 consecutive days. Tolerance can also occur in the absence of addiction.

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