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OPIOIDS (NARCOTIC ANALGETICS)
At present, they call so natural and synthetic preparations that are bound with morphinic (opioid) receptors in the brain and spinal cord. On this ground we refer here both the agonists, activating opioid receptors with which they are bound (morphine, meperidine, fentanvl. sufentanvl. alfentanyl. remifentanvO. and agonists-antagonists that exert their effect differently on various types of opiate receptors (nalbuphine, nalorphine, butorphanol. huprenorphine. pentazocine) and "pure" antagonist naloxone. All these agents may be administered intravenously, intramuscularly and subcutaneously, and fentanyl, in addition, in the form of "fentanyl sugar candy" perorally and in the form of "fentanyl plaster" percutaneously. Biotransformation occurs, mainly, in the liver, in which connection morphine forms a complex with glucuronic acid, meperidine is transformed by methylation with formation of normeperidine, capable to cause convulsions, and fentanyl, sufentanyl and alfentanyl form inactive metabolites. The kidneys excrete opioids partially in the unchanged form and as water-soluble metabolites. In renal failure an accumulation of the morphine metabolite — morphine-6-glucuronide that is a more potent opioid than morphine itself, causes a depression of CNS and respiration for many days. A new opioid — remifentanyl is rapidly hydrolyzed in the blood and tissues that completely eliminates the danger of cumulation both in repeated and prolonged stream administration and in the patients with hepatic and renal insufficiency. Whereas in intravenous injection opioids start to act practically just after their administration, after intramuscular injection a peak of concentration comes in 20-60 min., after subcutaneous one somewhat later, and in percutaneous administration of fentanyl, maximum concentration is observed in 14-24 hrs and maintained for a period of 72 hrs. Duration of maximum analgetic effect of opioids in single intravenous administration is given in Table 3. Recommended doses of preparations presented in the same Table, however, a final dosage must be implemented individually, taking into account clinical signs. Very high doses may be required in case of opioid addiction. Table 3 Дата добавления: 2015-02-05 | Просмотры: 770 | Нарушение авторских прав |