Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Tolbutamide is one of the first sulfonylureas, introduced in the 1950s: it closes potassium channels in the insulin-making beta cells of the pancreas so they release more insulin. It was used for type 2 diabetes and has largely been replaced by newer medicines. It was sold as Orinase.
Tolbutamide is broken down almost entirely by CYP2C9, so completely that researchers have used it as a test substance to measure CYP2C9 activity; people with the *3 version clear it much more slowly. The US FDA lists G6PD for tolbutamide, as sulfonylureas can cause haemolysis in people with G6PD deficiency. There is no CPIC or DPWG guideline.
Clinical guidelines that name a gene for Tolbutamide. They sort people into groups by the gene copies they carry.
US FDA: G6PD. Deficient with CNSHA · Deficient · Variable.
Every published finding on gene variants and Tolbutamide. 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.
CYP2C9 CYP2C9*1, CYP2C9*2, CYP2C9*3, CYP2C9*62: Level 3. Metabolism/PK. 3.
CYP2C9 rs9332239: Level 3. Other. 1.
CYP2C9 rs762081829: Level 3. Metabolism/PK. 1.
CYP2C9 rs771237265: Level 3. Metabolism/PK. 1.
Studies of how quickly the body processes this medication.
Studies of how well it worked 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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