Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Ondansetron is an anti-sickness medicine of the 5-HT3 antagonist group: it blocks serotonin receptors in the gut and in the brain's vomiting centre. It is used to prevent nausea and vomiting caused by chemotherapy, radiotherapy and surgery. It is sold as Zofran, among other names.
Ondansetron is broken down by several liver enzymes, including CYP2D6. People with extra working CYP2D6 copies (ultrarapid metabolizers) clear it faster, and studies found more vomiting after surgery and chemotherapy in them. CPIC has published a guideline on CYP2D6 and ondansetron. Studies have also looked at the transporter ABCB1 and the serotonin transporter gene SLC6A4, with weaker evidence.
Clinical guidelines that name a gene for Ondansetron. They sort people into groups by the gene copies they carry.
CPIC guideline: CYP2D6. CYP2D6 activity score 0 to 6 or more. Strong. 2017.
Every published finding on gene variants and Ondansetron. 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*2, CYP2D6*2xN, CYP2D6*4, CYP2D6*5, CYP2D6*10, CYP2D6*35xN: Level 1A · replicated. Efficacy: Vomiting. 3.
ABCB1 rs2032582: Level 3. Efficacy: Postoperative Nausea and Vomiting, Vomiting. 2.
ABCB1 rs1045642: Level 3. Efficacy: Postoperative Nausea and Vomiting, Vomiting. 2.
SLC6A4 rs1042173: Level 3. Efficacy: Alcohol abuse. 1.
Studies of how quickly the body processes this medication.
CYP2D6 CYP2D6*1, CYP2D6*1xN: CYP2D6 *1/*1xN is associated with increased metabolism of ondansetron.
Studies of how well it worked in people carrying a variant.
Studies of how much of the drug people needed or tolerated.
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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