Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Opioids are a class of pain medicines that act on the body's opioid receptors, mainly the mu receptor, in the brain, spinal cord and gut. The class includes morphine, codeine, oxycodone, hydrocodone, fentanyl, tramadol, methadone and others. They are used for moderate to severe pain and, some of them, for cough, diarrhoea or the treatment of opioid dependence. This page collects studies that looked at opioids as a group.
For the class as a whole, the most studied gene is OPRM1, which makes the mu opioid receptor; its A118G variant (rs1799971) has been linked in some studies to needing more opioid for the same pain relief. COMT, the transporter ABCB1 and dopamine receptor genes have also been studied, mostly for dose needs and dependence, with mixed results. The strongest gene evidence is for individual opioids rather than the class: CYP2D6 for codeine, tramadol and hydrocodone, each with its own page and guideline.
Every published finding on gene variants and Opioids. 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.
OPRM1 rs1799971: Level 3. Dosage: Pain, Pain, Postoperative. 8.
COMT rs4680: Level 3. Dosage: Pain, Pain, Postoperative. 6.
ABCB1 rs1045642: Level 3. Dosage: Pain, Pain, Postoperative. 6.
OPRM1 rs1799971: Level 3. Toxicity: adverse events, Nausea, Vomiting. 4.
Studies of how well it worked in people carrying a variant.
Studies of how much of the drug people needed or tolerated.
Studies that do not fall into the groups above.
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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