Articles: opioid-analgesics.
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Forty healthy, young volunteers received intravenously, in a double-blind and random fashion, 7.5 or 15 micrograms/kg of alfentanil, 1.5 or 3 micrograms/kg of fentanyl, or saline. The ventilatory response to CO2 was measured before and at 4, 20, 30, 50, 80, and 120 min post-treatment. Mental and psychomotor functions were measured before and at 10, 40, 100, 130, and 180 min post-treatment. ⋯ High-dose fentanyl caused more intense and prolonged mental effects than other treatments. Neither drug affected learning or recall, although high-dose fentanyl impaired motor activity. Nausea and vomiting rates were similar between high-dose alfentanil and low-dose fentanyl.
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Narcotics have been shown to act selectively upon nociceptive synaptic junctions in laminae 1 and 2 of the dorsal horn of the spinal cord. Subarachnoid or epidural injection of narcotics can produce selective segmental analgesia of great intensity and prolonged duration that is free of motor or sympathetic blockade. However, poorly lipid-soluble drugs, such as morphine, that tend to linger in the water phase of the CSF may spread rostrally to involve opiate receptors in brain stem nuclei. ⋯ Obstetrical pain is less amenable to this approach. Effective and safe management of acute pain requires that the patients be under adequate surveillance to avoid the danger of insidious respiratory depression. Chronic malignant pain is well controlled by relatively small doses of narcotic, and these patients can be managed at home on a long-term basis.
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The concept of multiple opioid receptors reconciles a large body of clinical and pharmacological data. Recent studies have shown that there are also multiple opioid binding sites. It would appear that there is considerable variability between species in both the specificity and selectivity of opioid receptors. ⋯ Already subspecies of mu, kappa, and sigma receptors are being postulated. Both pharmacological and neurochemical methods may reveal even more. Some of the newer kappa agonists differ in their pharmacology from the prototypic kappa agonist ethylketazocine.