Dependence with agonist-antagonist opioids

A low-efficacy opioid can reduce the effectiveness of a high-efficacy opioid by successfully competing with the latter for receptors. Partial agonist (agonist/antagonist) opioids, e.g. pentazocine, will also antagonise the action of other opioids, e.g. heroin, and may even induce the withdrawal syndrome in dependent subjects. 

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. 

Buprenorphine is derived from thebaine. It is a partial mu agonist with kappa antagonist activity. Buprenorphine has 25 to 50 times the potency of morphine. It is used to produce a longer-lasting analgesia than morphine. Effects of buprenorphine last longer because it is released more slowly from mu receptors than morphine. It is available as an injectable for intramuscular (IM) or intravenous administration in a 1-ml solution containing 0.3 mg buprenorphine (as buprenorphine HC1) for the relief of moderate to severe pain. It is also available to treat opioid dependence in the formulation of a tablet,51 alone or in combination with naloxone, in 2- or 8-mg... 

Patients who have received hydromorphone for long periods of time or those with confirmed opioid dependency should not receive the so-called agonist/antagonist analgesics, such as nalbuphine, pentazocine, butorphanol, dezocine, and buprenorphine. The use of these drugs in these patients can intensify withdrawal symptoms. 

Narcotic agonist-antagonists are less potent and have a lower dependency potential than opioids. Withdrawal symptoms from narcotic agonist-antagonists are not as severe as with narcotic agonists (narcotic analgesics). 

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