Injection of opiates

Contains more than a score of alkaloids, including morphine, narcotine, papaverine, and codeine, which act to relax smooth muscle, relieve pain, and cause sedation by depressant effect on cerebral cortex, hypothalamus, and medullary centers. It is indicated in the relief of moderate to severe pain associated with ureteral spasm not responsive to nonnarcotic analgesics and to space intervals between injections of opiates. 

If we are to harness the placebo effect and make use of it in clinical practice, we first have to understand how it works. A number of factors have been proposed as explanations of the placebo effect. These include the relationship between doctors and patients, the patient s beliefs and expectations, the production of opiates in the brain, and a phenomenon called classical conditioning, in which people come to associate pills and injections with therapeutic effects, just as Pavlov s dogs came to associate the sound of a bell with the presentation of food. In this chapter we look at how all of these processes combine to produce placebo effects, and we consider their implications for the treatment of depression. 

Decreased sensitivity to a drug, or tolerance, is seen with some drugs such as opiates and usually requires repeated administration of the drug. Tachyphylaxis, in contrast, is tolerance that develops rapidly, often after a single injection of a drug. In some cases, this may be due to what is termed as the dawn regulation of a drug receptor, in which the number of receptors becomes decreased. 

Injection of the opiate antagonist naloxone precipitates the somatic signs of nicotine withdrawal (Adams and Cicero 1998 Carboni et al. 2000 Malin et al. 1993a), but not affective signs, such as intracranial self-stimulation (ICSS) threshold elevation (Watkins et al. 2000). Yet naloxone injection in a nicotine-infused rat is robustly aversive (Ise et al. 2000 Watkins et al. 2000). Therefore, the somatic signs may actually correspond better than ICSS thresholds to an aversive motivational state. 

Narcotics Demerol Morphine Heroin Others Natural and synthetic opioids analgesics Oral or injected (IM, IV) Relaxation euphoria feelings of tranquility prevent onset of opiate withdrawal Physical dependence respiratory depression high potential for death due to overdose See Chapter 14... 

Small quantities of opiate injected intrathecally or epidurally produce segmental analgesia. This observation led to the clinical use of spinal and epidural opiates during surgical procedures and for the relief of postoperative and chronic pain. As with local anesthesia, analgesia is confined to sensory nerves that enter the spinal cord dorsal horn in the vicinity of the injection. Presynaptic opioid receptors inhibit the release of substance P and other neurotransmitters from primary afferents, whereas postsynaptic opioid receptors decrease the activity of certain dorsal horn neurons in the spinothalamic tracts. 

Anileridine, ethyl l-(4-amino phenethyl)-4 phenylisonipecotate is available in the form of its dihydrochloride for oral administration and as the phosphate for injection (Leritine ). Its analgesic potency is intermediate between that of meperidine and morphine. Similar to meperidine, it exerts mild antihistaminic and spasmolytic effects, but it is devoid of the constipating effect of opiates. Sedative and direct hypnotic effects are similar to those of meperidine but less than those of morphine. 

Opiate addiction has also helped spread diseases, such as the human immunodeficiency virus, hepatitis B virus, hepatitis C virus, and tuberculosis among addicts who inject the opiate drugs and share dirty needles. The rate of opiate-associated emergency hospital visits in recent years has significantly increased. Furthermore, the number of deaths related to those opiate overdoses has almost doubled in this period. All of these trends point to the significant social costs associated with opiate abuse in the United States. 

Since the early 1990s the prevalence of human immunodeficiency virus (HIV), hepatitis B and C viruses, and tuberculosis among people who inject opiate drugs has increased dramatically. The annual number of opiate-related emergency room visits has increased dramatically and the number of people who die each year as a result of abusing opiates has nearly doubled in recent years, further underscoring the human, economic, and societal costs of opiate addiction. 

Gustavsson E, Andersson M, Stephanson N, Beck O (2007) Validation of direct injection electrospray LC-MS/MS for confirmation of opiates in urine drag testing. J Mass Spectrom 42 881-889... 

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