The concern for prescription drug abuse has recently overshadowed that of illicit drug abuse, as the non-medical use of scheduled medications prescribed for pain, pain-related symptoms, and psychiatric disorders began rising in the mid-1990s. Non-medical use of prescription drugs was previously estimated in about 0.7 million individuals, 0.5 million of which used prescription pain relievers such as codeine, meperidine, morphine, fentanyl, hydro-morphone, hydrocodone, methadone, and oxycodone (Joranson et al. 2000). In 2003, the lifetime prevalence rates for non-medical use of opioids increased to about 3 million (Smith and Woody 2005). While opioid drug mentions decreased by 25% from 1990 to 1996, year 2000 and 2003 updates showed a significant increase in oxycodone mentions (Joranson et al. 2000, Office of Applied Studies, Substance Abuse and Mental Health Services Administration 2003). The prevalence of opioid abuse is now similar to that of cocaine and only second to that of marijuana. Consequent to this, the government has become more involved in trying to curb the growing menace of prescription drug abuse. But beyond regulatory oversight, the intrinsic difficulties of treating pain especially in individuals with history of substance abuse and in those with prescription drug abuse pose special dilemmas even for experienced practitioners. Non-medical users of prescription drugs have been described to be more likely Caucasian, use alcohol, cocaine, or heroin, or use needles to inject drugs compared to those who reported using illicit drugs only. Youths and young adults who used prescription drugs non-medically have a higher rate of other illicit drug use as well.
Use of opioids often leads to rapid tolerance and eventually to physical and psychosocial dependence. Physical dependence and withdrawal due to opioid use results from upreg-ulation of the cyclic aminophosphorase (cAMP) pathway at the locus coeruleus (Kasser et al. 1998). Unlike addiction which is a pathologic process, physical dependence is a natural expected physiologic response that can occur with use not only of opioids but also of ben-zodiazepines, alcohol, antidepressants, corticosteroids, diabetic agents, cardiac medications, and many other medications used in clinical medicine (Pastermark 2001). Tolerance is also a normal expected physiologic response that can occur with exposure to not only opioids but also certain class of drugs or substance like alcohol. Pain tolerance develops presumably as a result of decreased endogenous opioid release leading to the individual experiencing exaggerated pain. Administering the drug daily in increasing doses makes addiction to opioids occur more rapidly. Abrupt cessation or rapid dose reduction resulting in decreasing blood level of the drug and/or administration of an antagonist to the drug can produce a withdrawal syndrome that includes, but is not limited to, diaphoresis, nausea, vomiting, abdominal cramps, convulsions, or death (Nestler 2001). Chronic opioid use leads to cross tolerance to anesthetic and other depressant drugs as a result of chronic receptor stimulation. Opioids known to have been abused include codeine, meperidine, oxydocone, fentanyl, morphine, methadone, heroin, pentazocine, and propoxyphene. It is important to note, however, that most of these medications mentioned, though capable of producing physical dependence, are not associated with the disease of addiction (Portenoy 2007). A heroin addict, for example, is both physically dependent and addicted to the narcotic, while the pain patient taking opioids is physically dependent, but not necessarily addicted (Heit 2003, Pastermark 2001). Both will experience withdrawal if the drug is abruptly stopped, and both can exhibit tolerance to the drug.
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