Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Dextromethorphan is a cough suppressant that acts on the cough centre in the brain; at higher levels it blocks NMDA receptors. It is in many cold and cough remedies sold without prescription, and combined with quinidine (Nuedexta) it treats uncontrollable laughing or crying after brain injury; combined with bupropion it is used for depression. Robitussin is one brand.
Dextromethorphan is broken down by the liver enzyme CYP2D6 into dextrorphan, and it is so dependent on that enzyme that researchers use it as a test substance to measure a person's CYP2D6 activity. People with no working CYP2D6 copies (poor metabolizers) keep far higher dextromethorphan levels, which is why quinidine or bupropion, both CYP2D6 blockers, are paired with it in some products. Nearly all studies on this page concern CYP2D6; there is no CPIC or DPWG guideline.
Every published finding on gene variants and Dextromethorphan. Upload your DNA file to see which of these rows apply to you.
PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.
CYP2D6 CYP2D6*1, CYP2D6*2, CYP2D6*3, CYP2D6*4, CYP2D6*4x2, CYP2D6*4xN, CYP2D6*5, CYP2D6*6, CYP2D6*10, CYP2D6*10x2, CYP2D6*13, CYP2D6*14, CYP2D6*15, CYP2D6*17, CYP2D6*18, CYP2D6*21, CYP2D6*29, CYP2D6*31, CYP2D6*36, CYP2D6*40, CYP2D6*41, CYP2D6*42, CYP2D6*44, CYP2D6*49, CYP2D6*52, CYP2D6*55, CYP2D6*56, CYP2D6*59, CYP2D6*69, CYP2D6*84, CYP2D6*100, CYP2D6*101: Level 1B · replicated. Metabolism/PK. 52.
CYP2D6 CYP2D6*1, CYP2D6*7, CYP2D6*12, CYP2D6*26, CYP2D6*37, CYP2D6*47, CYP2D6*50, CYP2D6*51, CYP2D6*54, CYP2D6*62, CYP2D6*64, CYP2D6*71, CYP2D6*72, CYP2D6*75, CYP2D6*87, CYP2D6*89, CYP2D6*90, CYP2D6*91, CYP2D6*92, CYP2D6*93, CYP2D6*94, CYP2D6*95, CYP2D6*96, CYP2D6*97, CYP2D6*98, CYP2D6*114, CYP2D6*134, CYP2D6*153, CYP2D6*169: Level 3. Metabolism/PK. 7.
CYP2D6 rs750996195: Level 3. Metabolism/PK. 1.
CYP2D6 rs745746329: Level 3. Metabolism/PK. 1.
Studies of how quickly the body processes this medication.
Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.
More drugs from the same category
Advair (Corticosteroid + LABA)
Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.
Content updated September 2026.
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