Opioid analgesic drugs addiction

Moreover, there exist polymorphic MOP variants. An Asn40Asp polymorphism has been found with a high abundance in the Caucasian and Asian population. This receptor variant is less expressed in the brain and carrier of this polymorphism appears to need more opioids for analgesic treatment. There are many additional MOP polymorphisms with unknown functional significance. In spite of many studies there appears to exist no significant association of polymorphisms in the MOP gene and drug addiction [5]. 

The opioid analgesics are among the most effective drugs available for the suppression of cough. This effect is often achieved at doses below those necessary to produce analgesia. The receptors involved in the antitussive effect appear to differ from those associated with the other actions of opioids. For example, the antitussive effect is also produced by stereoisomers of opioid molecules that are devoid of analgesic effects and addiction liability (see below). 

Morphine was isolated from opium in 1806, which was a significant step in scientific pharmacology. For the first time, a powerful, pain-relieving medicine was available whose effects were predictable. However, it eventually became clear that the addictive potential of morphine is equal to that of opium, with many of the same side effects. Undaunted, scientists began the quest, which is ongoing, for the perfect opioid—a drug with the analgesic power of morphine, but with much milder side effects and little or no addictive potential. 

Although treatment of mild to moderate pain can typically be accomplished with nonnarcotic analgesics such as acetaminophen or aspirin, treatment of severe pain often requires use of an opioid analgesic such as morphine. These drugs are associated with serious side effects, however, most notably addiction liability and respiratory depression, which limit their clinical usefulness. Therefore there has been an intensive effort to find new analgesics that retain the effectiveness of morphine, but do not have the undesired side effects. As a result, a wide variety of compounds with opioid activity have been identified and significant strides have been made in understanding the mechanisms of opioid action. 

Tolerance, Dependence, and Addiction Liability. Patients treated with long-term opioid therapy often develop tolerance and usually become physically dependent on narcotic analgesics as well. Tolerance results when exposure to a drug results in its decreased effectiveness with time and larger doses are required to achieve the same response (26). Physical dependence is also an adaptive state that is characterized by a specific constellation of withdrawal symptoms that occur upon abrupt cessation or significant reduction in the dose of the opioid or administration of an opioid antagonist (26). Addiction, however, is distinct from physical dependence, and "the term addiction should never be used when physical dependence is meant" (22). The... 

Opioid analgesics are one of the few classes of medications available to treat severe levels of pain. Adding another drug to an opioid (compounding) may enhance analgesia, minimize adverse effects, reduce opioid tolerance and/or potentially deter overuse or abuse. Most astute chnicians recognize that concerns about abuse and addiction should not prevent the proper management of pain. In response. 

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