Articles: opioid-analgesics.
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Opioid receptors are described and differentiated by their affinities for specific agonists and antagonists. Their sites of action and receptor activities are discussed. Tachyphylaxis and tolerance are described and methods for overcoming these problems are recommended. Suggestions are made regarding future drugs to act at specific receptors.
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The discovery of opiate receptors and naturally occurring opiate-like substances in the central nervous system started a new era in pain control. Epidural and spinal opiates have been increasingly used since 1979. However, applying these analgesic techniques in obstetrics has been criticized because of possible side-effects on the mother and foetus. ⋯ The choice of a lipid-soluble opiate like fentanyl is safe. However, when considering new drugs, great care must be taken to avoid unforeseen problems. A good knowledge of the problem and a cautious approach combined with careful monitoring of the respiratory rate and adequacy of ventilation are the keys to the safe use of spinal and epidural opiates.