Delta-opioid receptor antagonists

Apigenin (4′,5,7-trihydroxyflavone), found in many plants, is a flavone compound that is the aglycone of several naturally occurring glycosides. It is a yellow crystalline solid that has been used to dye wool.

Naringenin is a flavanone from the flavonoid group of polyphenols. It is commonly found in citrus fruits, especially as the predominant flavonone in grapefruit.

Nalmefene, sold under the brand name Revex among others, is a medication that is used in the treatment of opioid overdose and alcohol dependence. Nalmefene belongs to the class of opioid antagonists and can be taken by mouth, administered by injection, or delivered through nasal administration.

Diprenorphine (brand name Revivon; former developmental code name M5050), also known as diprenorfin, is a non-selective, high-affinity, weak partial agonist of the μ- (MOR), κ- (KOR), and δ-opioid receptor (DOR) (with equal affinity) which is used in veterinary medicine as an opioid antagonist. It is used to reverse the effects of super-potent opioid analgesics such as etorphine and carfentanil that are used for tranquilizing large animals. The drug is not approved for use in humans.

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.

JDTic is a selective, long-acting ("inactivating") antagonist of the κ-opioid receptor (KOR). JDTic is a 4-phenylpiperidine derivative, distantly related structurally to analgesics such as pethidine and ketobemidone, and more closely to the MOR antagonist alvimopan. In addition, it is structurally distinct from other KOR antagonists such as norbinaltorphimine. JDTic has been used to create crystal structures of KOR [ ].

Naltrindole is a highly potent, highly selective delta opioid receptor antagonist used in biomedical research. In May 2012 a paper was published in Nature with the structure of naltrindole in complex with the mouse δ-opioid G-protein coupled receptor, solved by X-ray crystallography.

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.