IBNtxA, or 3-iodobenzoyl naltrexamine, is an atypical opioid

analgesic An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...

drug derived from naltrexone. In animal studies it produces potent analgesic effects that are blocked by

levallorphan Levallorphan ( INN, BAN) (brand names Lorfan, Naloxifan, Naloxiphan), also known as levallorphan tartrate (USAN), is an opioid modulator of the morphinan family used as an opioid analgesic and opioid antagonist/antidote. It acts as an antagonist ...

and so appear to be μ-opioid mediated, but it fails to produce constipation or

respiratory depression Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (''hypo'' meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapnia ...

, and is neither rewarding or aversive in

conditioned place preference Conditioned place preference (CPP) is a form of Pavlovian conditioning used to measure the motivational effects of objects or experiences. This motivation comes from the pleasurable aspect of the experience, so that the brain can be reminded of th ...

protocols. These unusual properties are thought to result from agonist action at a splice variant or

heterodimer In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has ...

of the μ-opioid receptor, rather than at the classical full length form targeted by conventional opioid drugs. In the Radioligand binding assay it has shown to have affinities of 0.11nM at the MOR, 0.24nM at the DOR and 0.03nM at the KOR and in the Hot- Plate Assay it is shown to be around 20x more potent than morphine. Azido Aryl Analogues of IBNtxA retain significant activity at the MOR.

References

Benzamides Mu-opioid receptor agonists Phenols Semisynthetic opioids {{analgesic-stub