Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Doxepin is a tricyclic antidepressant (TCA) that also strongly blocks histamine. At usual antidepressant doses it is used for depression and anxiety; at very low doses it is used for trouble staying asleep, and as a cream for itching. It is sold as Sinequan and, for sleep, Silenor, among other names.
CYP2C19 turns doxepin into nordoxepin, which is also active, and CYP2D6 breaks both down further. People with little or no CYP2D6 activity can have several times higher levels, and the US drug label for the sleep product notes that CYP2C19 and CYP2D6 poor metabolizers may have higher levels. CPIC (for the tricyclics as a group) and DPWG have published guidelines, and the US FDA lists an effect on drug levels for both genes.
Clinical guidelines that name a gene for Doxepin. They sort people into groups by the gene copies they carry.
DPWG guideline: CYP2D6. CYP2D6 activity score 0 to 6 or more. 2026.
Every published finding on gene variants and Doxepin. 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*1xN, CYP2D6*2xN, CYP2D6*3, CYP2D6*4, CYP2D6*5, CYP2D6*9, CYP2D6*10, CYP2D6*35, CYP2D6*35xN, CYP2D6*41: Level 1A · replicated. Metabolism/PK. 6.
CYP2C19 CYP2C19*1, CYP2C19*2: Level 1A · replicated. Metabolism/PK. 1.
CYP2C9 CYP2C9*1, CYP2C9*3: Level 3. Efficacy. 1.
Studies of how quickly the body processes this medication.
CYP2D6 CYP2D6*3, CYP2D6*4: CYP2D6 *3/*4 is associated with decreased metabolism of doxepin.
Studies of how much of the drug people needed or tolerated.
Studies of side effects in people carrying a variant.
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
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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