Opioid agonist-antagonist drugs

The agonist-antagonists drug can cause opioid witii-drawal symptoms in tiiose who are physically dependent on die opioids. There is an increased risk of respiratory... 

Hoskin, P.J., Hanks, G.W. Opioid agonist-antagonist drugs in acute and chronic pain states, Drugs 1991, 41, 326-344. 

When allergies occur with one opioid, a drug from a different structural class of opioids may be tried with caution. For these purposes, the mixed agonist/antagonist class behaves most like the morphine-like agonists. 

The treatment of opioid abuse and dependence aims also at preventing the social complications of abuse, especially infections linked to parenteral administration (HIV and HepB). It relies on the use of substimtive drugs that can be either pure agonists, or partial agonist-antagonists (methadone, buprenor-phine, naltrexone), with the objective of limiting receptor desensitization and the development of tolerance. Any success in the treatment of opiate dependence may stem as much from the re-establishment of healthcare contact and social reinsertion as from any treatment induced decrease in the abuse behaviour itself. 

Bowdle, T.A. (1998) Adverse effects of opioid agonists and agonist-antagonists in anaesthesia. Drug Saf. 19 173-189. 

Endogenous opioid peptides. Extensive processing is also involved in formation of analgesic opioid peptides, which are present naturally in the brain (see also Section B). Tire formation of (1-endorphin in the hypothalamus from prepro-opiomelanocortin (Fig. 30-2) has already been mentioned. Prior to the discovery of P-endorphin, the pentapeptides Met-enkephalin and Leu-enkephalin (Table 30-4) were discovered and were found to compete with opiate drugs for receptors in the brain. Tire larger P-endorphin, which contains the Met-enkephalin sequence at its N terminus, is a far more potent opiate antagonist than are the enkephalins. Since the Met-enkephalin sequence within P-endorphin is not flanked by basic residues, it apparently is normally not released. Two other recently discovered brain peptides are endomorphin-1 (YPWF-NH2) and endomorphin-2 (YPFF-NH2). They are also potent agonists for the opioid receptors, especially the p receptor (see Section B,10).,61a,61b... 

Preston, K. et al., Drug discrimination in human post-addicts agonist/antagonist opioids, NIDA Res. Mon., 81, 209, 1988. 

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