An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors.
The ∆-opioid receptor, also known as delta opioid receptor or simply delta receptor, abbreviated DOR or DOP, is an inhibitory 7-transmembrane G-protein coupled receptor coupled to the G protein Gi/G0 and has enkephalins as its endogenous ligands. The regions of the brain where the ∆-opioid receptor is largely expressed vary from species model to species model. In humans, the ∆-opioid receptor is most heavily expressed in the basal ganglia and neocortical regions of the brain.
PB-28 is an agonist of the sigma-2 receptor.
Dynorphin A is a dynorphin, an endogenous opioid peptide that activates the κ-opioid receptor. Its amino acid sequence is Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys.
SNC-80 is an opioid analgesic compound that selectively activates μ–δ opioid receptor heteromers and is used in scientific research. It was discovered in 1994.
Pravadoline (WIN 48,098) is an antinflammatory and analgesic drug with an IC50 of 4.9 μM and a Ki of 2511 nM at CB1, related in structure to nonsteroidal anti-inflammatory drugs (NSAIDs) such as indometacin. It was developed in the 1980s as a new antiinflammatory and prostaglandin synthesis inhibitor, acting through inhibition of the enzyme cyclooxygenase (COX).
BU-48 is a drug that is used in scientific research. It is from the oripavine family, related to better-known drugs such as etorphine and buprenorphine.
Azaprocin is a drug which is an opioid analgesic with approximately ten times the potency of morphine, and a fast onset and short duration of action. It was discovered in 1963, but has never been marketed.
7-Spiroindanyloxymorphone (SIOM) is a drug that is used in scientific research. It is a selective δ-opioid agonist. It is a derivative of oxymorphone.
Quipazine is a serotonergic drug of the piperazine group which is used in scientific research. It was originally intended as an antidepressant but never developed for medical use.
TAN-67 (SB-205,607) is an opioid drug used in scientific research that acts as a potent and selective δ-opioid agonist, selective for the δ1 subtype. It has analgesic properties and induces dopamine release in nucleus accumbens. It also protects both heart and brain tissue from hypoxic tissue damage through multiple mechanisms involving among others an interaction between δ receptors and mitochondrial K(ATP) channels.
Naltriben is a potent and selective antagonist for the delta opioid receptor, which is used in scientific research. It has similar effects to the more widely used δ antagonist naltrindole, but with different binding affinity for the δ1 and δ2 subtypes, which makes it useful for distinguishing the subtype selectivity of drugs acting at the δ receptors. It also acts as a κ-opioid agonist at high doses.
Chlornaltrexamine is an irreversible mixed agonist–antagonist for μ-opioid receptors, which forms a covalent bond to the binding site. It is 22 times more potent than morphine. Its alkylating group is a bis(chloroalkyl)amino-residue similar to that of the nitrogen mustards.
GR-89696 is a drug which acts as a highly selective κ-opioid agonist. It has been studied in various animal species, and has been described as selective for the κ2 subtype. Recent studies have suggested that GR-89696 and related κ2-selective agonists may be useful for preventing the itching which is a common side effect of conventional opioid analgesic drugs, without the additional side effects of non-selective kappa agonists. The structure bound to the κ-opioid receptor has been reported.
Org 28312 is a drug developed by Organon International which acts as a potent cannabinoid receptor full agonist at both the CB1 and CB2 receptors. It was developed with the aim of finding a water-soluble cannabinoid agonist suitable for intravenous use as an analgesic, but did not proceed to human trials, with the related compound Org 28611 chosen instead due to its better penetration into the brain. The structure-activity relationships of these compounds have subsequently been investigated further leading to the development of a number of more potent analogues, derived by cyclisation around the indole or piperazine rings.
MT-45 (IC-6) is an opioid analgesic drug invented in the 1970s by Dainippon Pharmaceutical Co. It is chemically a 1-substituted-4-(1,2-diphenylethyl)piperazine derivative, which is structurally unrelated to most other opioid drugs. Racemic MT-45 has around 80% the potency of morphine, with almost all opioid activity residing in the (S) enantiomer. It has been used as a lead compound from which a large family of potent opioid drugs have been developed, including full agonists, partial agonists, and antagonists at the three main opioid receptor subtypes. Fluorinated derivatives of MT-45 such as 2F-MT-45 are significantly more potent as μ-opioid receptor agonists, and one of its main metabolites 1,2-diphenylethylpiperazine also blocks NMDA receptors.
AD-1211 is an opioid analgesic drug invented in the 1970s by Dainippon Pharmaceutical Co. It is chemically a 1-substituted-4-prenyl-piperazine derivative, which is structurally unrelated to most other opioid drugs. The (S)-enantiomers in this series are more active as opioid agonists, but the less active (R)-enantiomer of this compound, AD-1211, is a mixed agonist–antagonist at opioid receptors with a similar pharmacological profile to pentazocine, and has atypical opioid effects with little development of tolerance or dependence seen after extended administration in animal studies.
Mitragynine pseudoindoxyl is a rearrangement product of 7-hydroxymitragynine. It is an analgesic being more potent than morphine.
Bucinnazine is an opioid analgesic drug that was widely used in China to treat pain in cancer patients as of 1986. It is one of the most potent compounds among a series of piperazine-amides first synthesized and reported in Japan in the 1970s. Bucinnazine has analgesic potency comparable to that of morphine but with a relatively higher therapeutic index.
Diphenpipenol is an opioid analgesic drug invented in the 1970s by Dainippon Pharmaceutical Co. It is chemically a 1-substituted-4-(1,2-diphenylethyl)piperazine derivative related to compounds such as MT-45 and AD-1211, but diphenpipenol is the most potent compound in the series, with the more active (S) enantiomer being around 105 times the potency of morphine in animal studies. This makes it a similar strength to fentanyl and its analogues, and consequently diphenpipenol can be expected to pose a significant risk of producing life-threatening respiratory depression, as well as other typical opioid side effects such as sedation, itching, nausea and vomiting.
