Dextromethorphan
DelsymPubChem CID 5360696 · 3D model
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Calms an overactive brainstem cough reflex as an over-the-counter cough suppressant — and, at the receptor level, blocks the same general kind of nerve-signaling channel as ketamine, also on this site, much more weakly, the basis for the unrelated antidepressant combination Auvelity.
How it works
The 'DM' in cough syrup is believed to work by calming down a cough-control switch in the brainstem, though the actual FDA label on the bottle just says 'cough suppressant' and doesn't explain how. Separately, and unrelated to treating coughs, dextromethorphan also blocks the same general kind of brain-signaling channel that ketamine does, also on this site, though much more weakly, so it doesn't cause ketamine's dissociative effects at normal cough-syrup doses, and activates another receptor called sigma-1. That combination is why dextromethorphan, paired with the antidepressant bupropion, forms Auvelity, a completely different, FDA-approved prescription product for depression, not a cough medicine.
What it’s used for
Sold over the counter as a cough suppressant in products like Delsym, for temporary relief of cough from a cold or minor throat and airway irritation. The same ingredient, combined with the antidepressant bupropion in a separate prescription product called Auvelity, is FDA-approved for major depression and for agitation in Alzheimer's dementia, but that's a different drug product with its own approval.
- Mechanism
- Central cough suppressant (NMDA receptor antagonist / sigma-1 receptor agonist)
- Drug class
- Small molecule
- Therapeutic area
- Respiratory