Methadone

Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.

About Methadone

What it is

Methadone is a long-acting opioid. It also blocks NMDA receptors, and it can lengthen the QT interval of the heartbeat. It is sold as Dolophine and Methadose, among other names.

How genes come into it

Methadone's blood levels differ widely between people, and the strongest genetic link is CYP2B6, the main enzyme that breaks it down: the slow *6 version raises levels of the more active form. Over 300 studies have also looked at the transporter ABCB1, the opioid receptor genes OPRM1 and OPRD1, CYP2D6 and CYP2C19, and dopamine genes, with mixed results. There is no CPIC or DPWG guideline.

What research found

Every published finding on gene variants and Methadone. Upload your DNA file to see which of these rows apply to you.

Rated evidence (100 rated variants)

PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.

CYP2B6 CYP2B6*1, CYP2B6*4, CYP2B6*6, CYP2B6*18: Level 2A · replicated. Metabolism/PK: Heroin Dependence, Opioid-Related Disorders. 9.

ABCB1 rs1045642: Level 3. Metabolism/PK: Opioid-Related Disorders. 7.

CYP2D6 CYP2D6*1, CYP2D6*1xN, CYP2D6*3, CYP2D6*4, CYP2D6*6: Level 3. Metabolism/PK. 7.

CYP2B6 rs3745274: Level 3. Dosage: Heroin Dependence, Opioid-Related Disorders. 6.

Metabolism (80 findings)

Studies of how quickly the body processes this medication.

low activity: CYP3A low activity is associated with increased trough concentration of methadone as compared to CYP3A high activity.

rs17180299: Genotypes AG + GG are associated with increased concentrations of methadone in people with Opioid-Related Disorders as compared to genotype AA.

ABCB1 rs1045642: Genotype AA is associated with increased concentrations of methadone as compared to genotypes AG + GG.

ABCB1 rs1045642: Allele A is associated with decreased concentrations of methadone in people with Opioid-Related Disorders as compared to allele G.

Response (82 findings)

Studies of how well it worked in people carrying a variant.

ALDH5A1 rs2760118: Genotypes CT + TT is associated with decreased response to methadone in people with Opioid-Related Disorders as compared to genotype CC.

BDNF rs11030119: Allele G is associated with decreased response to methadone in people with Opioid-Related Disorders as compared to allele A.

BDNF rs2030324: Allele G is associated with decreased response to methadone in people with Opioid-Related Disorders as compared to allele A.

BDNF rs988748: Allele C is associated with decreased response to methadone in people with Opioid-Related Disorders as compared to allele G.

Dosing (187 findings)

Studies of how much of the drug people needed or tolerated.

ABCB1 rs1045642: Allele A is associated with decreased dose of buprenorphine, dihydrocodeine, fentanyl, hydromorphone, methadone, morphine, oxycodone, piritramide, tilidine or tramadol in people with Pain as compared to allele G.

ABCB1 rs1045642: Genotype AA is associated with increased dose of methadone in people with Heroin Dependence as compared to genotype GG.

ABCB1 rs1128503: Genotype AA is associated with increased dose of methadone in people with Heroin Dependence as compared to genotypes AG + GG.

ABCB1 rs2032582: Genotype CC is associated with decreased dose of methadone in people with Heroin Dependence as compared to genotypes AA + AC.

Side effects (1 finding)

Studies of side effects in people carrying a variant.

CYP2B6 CYP2B6*6: CYP2B6 *6/*6 is associated with decreased metabolism of methadone in children with Pain, Postoperative and Scoliosis.

Other findings (2 findings)

Studies that do not fall into the groups above.

DRD2 rs6275: Genotypes AA + AG are associated with increased dose of methadone in people with treatment for heroin addiction as compared to genotype GG.

KCNJ6 rs2070995: Genotype TT is associated with increased dose of methadone in people with Substance-Related Disorders as compared to genotypes CC + CT.

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.

Related Drugs

More drugs from the same category

Alfenta (Opioids)

Codeine (Opioids)

Demerol (Opioids)

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.

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Content updated September 2026.

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