|Systematic (IUPAC) name|
|Mol. mass||283.41 g/mol|
Dextrallorphan (DXA) is a drug of the morphinan class used in scientific research. It acts as a σ1 receptor agonist and NMDA receptor antagonist. It has no significant affinity for the σ2, μ-opioid, or δ-opioid receptor, or for the serotonin or norepinephrine transporter. As an NMDA receptor antagonist, in vivo, it is approximately twice as potent as dextromethorphan, and five-fold less potent than dextrorphan.
Research using Dextrallorphan dates back to at least 1955, where researchers used it in a study that looked at the relationship between analgetics and acetylcholine metabolism. This study specifically looked to determine the concentration required for morphine and similar compounds, like dextrallorphan, to inhibit enzymatic activity in bovine erythrocytes, rat brain, dog serum, and the muscular wall of dog intestine. It was found that dextrallorphan inhibited 25% of bovine erythrocyte cholinesterase at a dose of 10-3 mole/liter, which corresponds to a concentration of up to 0.2 mg/kg in dog intestine. However, at this dose the drug showed no effect on the gut tone. In the same study, dextrallorphan was classified as a potent inhibitor of the intestinal and red blood cell cholinesterase based on the concentration of the drug needed to inhibit these enzymes in the cholinesterase preparations from the animals systems utilized. Simultaneously, dextrallorphan showed no analgesia and no change in intestinal tone. With these results dextrallorphan helped proved that there is no correlation between the inhibition of cholinesterase systems and analgetic or intestinal effects. 
In 1979, dextrallorphan was found to have a half maximal inhibitory concentration (IC50) for binding to the pituitary and brain receptor of 10,000 ± 1000 nM and 10,000 ± 1500 nM, respectively. While its stereoisomer, levellorphan, had a 10,000 times more potent dose, thus proving that binding to these receptors is stereospecific. 
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