Once Pure agent scheme of presentation is executed it becomes very easy to deal with all the actions of the drugs of various classes of opioids, including pure agonist opioid .
While understanding the pharmacological, systemic effect of these drugs it is logically possible to fix the action as per the neuroanatomical site of origin of that action.
The examples of pure agonist opioid are: Morphine (naturally occurring drug), diacetylmorphine (heroin—semi synthetic agent), and fentanyl and its congeners (synthetic compounds). All of these are pure µ1, and µ2 agonists.
The prototype of these groups is morphine so drugs like codeine, heroin, and fentanyl follow similar pharmacological spectrum as that of morphine, with slight individual variations.
Pure agonist opioid has very high affinity for these receptors and all of them act through endogenous ligand β-endorphin. Some of the actions may also be mediated through δ receptors.
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