Psychological dependence, opioids

Finally, there is little or no clinical evidence that morphine causes psychological dependence or drug-seeking behaviour, tolerance or problematic respiratory depression in patients. These events simply do not occur when opioids are used to control pain. The reason is likely to be that the actions of morphine and the context of its use in a person in pain are neurobiologically quite different from the effects of opioids in street use. These actions of opioids are described in more detail in Chapter 23. 

The antipsychotics do not produce a ciassic withdrawai syndrome of the type seen with barbiturates or opioids nor do they produce psychological dependency, as seen with psychostimuiants (e.g., cocaine, amphetamine). Addicts and patients both dislike these drugs and do not spontaneously increase their dose. Indeed, they are more likely to discontinue them without medical advice. 

The most widely used approach to treating opioid addiction is methadone maintenance. Methadone, shown in Figure 14.44, is a synthetic opioid derivative that has most of the effects of other opioids, including euphoria, but differs in that it retains much of its activity when taken orally. This means that doses are very easy to control and monitor. The withdrawal symptoms of methadone are also far less severe, and the addict may be slowly weaned off the opioid without excessive stress. An addict may be freed of physical dependence in a matter of months. The psychological dependence, however, usually persists throughout the individual s life, which is why the relapse rate is so high. 

Neurotransmission events involved in the sensation of reward are also important. Alcohol affects local concentrations of serotonin, opioids, and dopamine—neurotransmitters involved in brain reward circuits. Alcohol also has complex effects on the expression of receptors for these neurotransmitters and their signaling pathways. The discovery that naltrexone, a nonselective opioid receptor antagonist, helps patients who are recovering from alcoholism abstain from drinking supports the idea that the neurochemical reward system is shared by drugs associated with physical and psychological dependence. 

It has been suggested that the risk of producing opioid dependence in the medical setting is greater in those who prescribe and administer them than in those who receive them (8). The likelihood of dependence in patients treated with opioids has been examined. In the treatment of cancer pain, tolerance and physical dependence occur but psychological dependence (addiction) is rare (9,10). 

Schedule II High risk for abuse. Can lead to physical and psychological dependence. Can be used for medicinal purpose. Includes opioids, barbiturates, and stimulants. 

What Schedule II medications are at high risk for abuse, and physical and psychological dependence Opioids, barbiturates, and stimulants that are not combined with other medication are at high risk for abuse, and physical and psychological dependence. 

In an interview study (Robson and Bruce 1997), the dependence potential of various street drugs was assessed in 201 problem and 380 social users of heroin, cocaine or amphetamine using the well-validated Severity of Dependence Scale (SDS). Scores (maximum = 15) in the problem group were 12.9 for heroin, 9.6 for other opioids, 6.1 for amphetamine and 5.5 for crack cocaine. All of these scores were consistent with findings in other studies. Cannabis SDS score was 2.6 and comparable with those of LSD (3.1) and ecstasy (1.3), two drugs that are generally not associated with physical or psychological dependence. In the parallel sample of social users, the cannabis SDS was similar at 3.4. 

Both physical and psychological dependence on opioid analgcsic-s gradually develops and sudden iciminaiion of drag administration precipitates a withdrawal syndrome (Chapter 31). 

Four principal opioid receptor subtypes, designated as mu, kappa, delta, and sigma, have been characterized [1,2]. A newer receptor classification system utilizes labels OPRj, OPR and OPR, which correspond to mu, kappa, and delta receptors respectively [1,3,8]. Mu receptors (OPR ) mediate supraspinal analgesia, as well as respiratory depression, nausea and vomiting, miosis and bowel hypomotil-ity. Mu receptors also mediate euphoria and physical and psychological dependence, and are responsible for the increased release of prolactin and growth hormone [1,2]. 

Unlike opioids, naproxen does not cause physical or psychological dependency, severe cognitive dysfunction, excessive nausea, vomiting, or constipation... 

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