Β-Chlornaltrexamine
β-Chlornaltrexamine is a non-selective irreversible antagonist of the μ-opioid receptor, the δ-opioid receptor, and the κ-opioid receptor, 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 bisamino-residue similar to that of the nitrogen mustards.
The drug was first described by 1978. It should not be confused with its epimer and related drug α-chlornaltrexamine, which is likewise predominantly an irreversible antagonist of the opioid receptors but also shows some irreversible mixed agonist–antagonist activity.