Irreversible agonists

Oxymorphazone is an opioid analgesic drug related to oxymorphone. Oxymorphazone is a potent and long acting μ-opioid agonist which binds irreversibly to the receptor, forming a covalent bond which prevents it from detaching once bound. This gives it an unusual pharmacological profile, and while oxymorphazone is only around half the potency of oxymorphone, with higher doses the analgesic effect becomes extremely long lasting, with a duration of up to 48 hours when administered intraventricularly. However, tolerance to analgesia develops rapidly with repeated doses, as chronically activated opio

β-Chlornaltrexamine (β-CNA) is a non-selective irreversible antagonist of the μ-opioid receptor (MOR), the δ-opioid receptor (DOR), and the κ-opioid receptor (KOR), which forms a covalent bond to the binding sites of these receptors and has ultra-long-lasting opioid antagonist effects. Although it is predominantly antagonistic, β-CNA also shows some irreversible mixed agonist–antagonist activity at the MOR and KOR and some associated analgesic effects. Its alkylating group is a bis(chloroalkyl)amino-residue similar to that of the nitrogen mustards.

right|thumb|250px|class=skin-invert-image|Metaphit as a methanesulfonate salt

type of agonist that binds permanently to a receptor in such a manner that the receptor is permanently activated. It is distinct from a mere (reversible) agonist in that the association of an agonist to a receptor is reversible