An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors.
Naloxone and naltrexone are commonly used opioid antagonist drugs which are competitive antagonists that bind to the opioid receptors with higher affinity than agonists but do not activate the receptors. This effectively blocks the receptor, preventing the body from responding to opioids and endorphins.
Some opioid antagonists are not pure antagonists but do produce some weak opioid partial agonist effects, and can produce analgesic effects when administered in high doses to opioid-naive individuals. Examples of such compounds include nalorphine and levallorphan. However, the analgesic effects from these specific drugs are limited and tend to be accompanied by dysphoria, most likely due to additional agonist action at the κ-opioid receptor. As they induce opioid withdrawal effects in people who are taking, or have recently used, opioid full agonists, these drugs are generally considered to be antagonists for practical purposes.
The weak partial agonist effect can be useful for some purposes, and has previously been used for purposes such as long-term maintenance of former opioid addicts using nalorphine, however it can also have disadvantages such as worsening respiratory depression in patients who have overdosed on non-opioid sedatives such as alcohol or barbiturates. On the other hand, Naloxone has no partial agonist effects, and is in fact a partial inverse agonist at μ-opioid receptors, and so is the preferred antidote drug for treating opioid overdose.
Naltrexone is also a partial inverse agonist, and this property is exploited in treatment of opioid addiction, as a sustained course of low-dose naltrexone can reverse the altered homeostasis which results from long-term abuse of opioid agonist drugs. This is the only treatment available which can reverse the long-term after effects of opioid addiction known as post acute withdrawal syndrome, which otherwise tends to produce symptoms such as depression and anxiety that may lead to eventual relapse.
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Couvre les interactions protéiques, la transduction des signaux, les neurotransmetteurs et les concepts pharmacologiques tels que les agonistes et les antagonistes.
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An opioid overdose is toxicity due to excessive consumption of opioids, such as morphine, codeine, heroin, fentanyl, tramadol, and methadone. This preventable pathology can be fatal if it leads to respiratory depression, a lethal condition that can cause hypoxia from slow and shallow breathing. Other symptoms include small pupils (with the exception of pethidine, where there may be dilated pupils), and unconsciousness, however its onset can depend on the method of ingestion, the dosage and individual risk factors.
Le carfentanil ou carfentanyl, aussi connu comme le 4-carbométhoxyfentanyl, est un opioïde synthétique à l'effet plus intense que le fentanyl et plus intense que la morphine, ce qui en fait un des opioïdes les plus puissants disponibles dans le commerce, sous l'appellation Wildnil. Il est utilisé essentiellement sous forme de citrate comme anesthésique général pour la sédation des gros mammifères, tels que éléphants, rhinocéros, bisons, morses, ours blancs Pour une chèvre sauvage, par exemple, une injection intramusculaire de provoque la sédation de l'animal après , avec une demi-vie de .
L'addiction, , ou assuétude, est l'envie répétée et irrépressible de faire ou de consommer quelque chose en dépit de la motivation et des efforts du sujet pour s'y soustraire. L'anglicisme addiction désigne tout attachement nocif à une substance ou à une activité. Le terme plus ancien d’assuétude est d'usage courant dans certaines régions de la francophonie, notamment au Québec. Dans d'autres régions, il est vieilli, mais reste parfois utilisé pour qualifier des dépendances faibles comme celle au chocolat.
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