Opioid tolerance psychological dependence

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. 

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). 

Psychological and physical dependence may occur. Tolerance may develop, resulting in the need for higher and more frequent dosing. Some oral pentazocine preparations also contain naloxone (an opioid antagonist) to reduce parenteral abuse. Naloxone does not affect the efficacy of pentazocine administered by the oral route naloxone does inhibit pentazocine s opioid effect if tablets are solubilized and injected. Pentazocine may be abused as a heroin alternative or in combination with other drugs. The most publicized combination was T s and Blues ... 

Opioid analgesic prototype strong mu receptor agonist. Poor oral bioavailability. Tox constipation, emesis, sedation, respiratory depression, miosis, and urinary retention. Tolerance may be marked high potential for psychologic and physiologic dependence. Additive effects with other CNS depressants. 

---