Dextrorphan
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Dextrorphan (DXO) is a psychoactive drug of the morphinan class which acts as an antitussive or cough suppressant and in high doses a dissociative hallucinogen. It is the dextrorotatory enantiomer of racemorphan; the levorotatory enantiomer is levorphanol. Dextrorphan is produced by O-demethylation of dextromethorphan by CYP2D6. Dextrorphan is an NMDA antagonist and contributes to the psychoactive effects of dextromethorphan.[1]
Pharmacology
Pharmacodynamics
| Site | Ki (nM) | Species | Ref |
|---|---|---|---|
| NMDAR (MK-801) |
486–906 | Rat | [3] |
| σ1 | 118–481 | Rat | [3] |
| σ2 | 11,325–15,582 | Rat | [3] |
| MOR | 420 >1,000 |
Rat Human |
[3][6] |
| DOR | 34,700 | Rat | [3] |
| KOR | 5,950 | Rat | [3] |
| SERT | 401–484 | Rat | [3] |
| NET | ≥340 | Rat | [3] |
| DAT | >1,000 | Rat | [3] |
| 5-HT1A | >1,000 | Rat | [3] |
| 5-HT1B/1D | 54% at 1 μM | Rat | [3] |
| 5-HT2A | >1,000 | Rat | [3] |
| α1 | >1,000 | Rat | [3] |
| α2 | >1,000 | Rat | [3] |
| β | 35% at 1 μM | Rat | [3] |
| D2 | >1,000 | Rat | [3] |
| H1 | 95% at 1 μM | Rat | [3] |
| mAChRs | 100% at 1 μM | Rat | [3] |
| nAChRs | 1,300–29,600 (IC50) |
Rat | [3] |
| VDSCs | ND | ND | ND |
| Values are Ki (nM), unless otherwise noted. The smaller the value, the more strongly the drug binds to the site. | |||
The pharmacology of dextrorphan is similar to that of dextromethorphan (DXM). However, dextrorphan is much more potent as an NMDA receptor antagonist and much less active as a serotonin reuptake inhibitor, but retains DXM's activity as a norepinephrine reuptake inhibitor.[7] It also has more affinity for the opioid receptors than dextromethorphan, significantly so at high doses.
Pharmacokinetics
Dextrorphan has a notably longer elimination half-life than its parent compound, and therefore has a tendency to accumulate in the blood after repeated administration of normally dosed dextromethorphan formulations.Script error: No such module "Unsubst". It is further converted to 3-HM by CYP3A4 or glucuronidated.[8]
Society and culture
Legal status
Dextrorphan was formerly a Schedule I controlled substance in the United States, but was unscheduled on October 1, 1976.[9]
Research
Dextrorphan was under development for the treatment of stroke, and reached phase II clinical trials for this indication, but development was discontinued.[10]
Environmental presence
In 2021, dextrorphan was identified in >75% of sludge samples taken from 12 wastewater treatment plants in California. The same study associated dextrorphan with estrogenic activity by using predictive modelling, before observing it in in vitro.[11]
See also
- Cough syrup
- Racemorphan; Levorphanol
- Noscapine
- Codeine; Pholcodine
- Dextromethorphan; Dimemorfan
- Butamirate
- Pentoxyverine
- Tipepidine
- Cloperastine
References
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