Sulfonamides
Severe
Textbook
Enhanced action of tolbutamide, potentially leading to hypoglycemia.
Source: KDT 7e
Drug reference
Tolbutamide
Sulfonylurea · Antidiabetic
SulfonylureaAntidiabetic
CDSCO approvedSchedule H
EXCRETION
—
not curated
INTERACTIONS
12 major
SEVERE in our sources
PREGNANCY
—
not curated
Top interactionssee all 12 →
- SulfonamidesSevereTextbookKDT 7e
- Aminolevulinic AcidSevereDatabaseDDInter
- CinoxacinSevereDatabaseDDInter
- CiprofloxacinSevereDatabaseDDInter
Mechanism
Tolbutamide, a sulfonylurea, stimulates insulin secretion from pancreatic beta cells, leading to increased plasma-insulin concentrations. This action results in the reduction of blood glucose levels. This increase in insulin is also associated with modest weight gain.
Indications
Type 2 diabetes mellitus (as monotherapy, or in combination with metformin, a dipeptidylpeptidase-4 inhibitor, pioglitazone, or a sodium glucose co-transporter 2 inhibitor)type 2 diabetes mellitus
Dosing
- Adult
- 0.5-3 g daily
- Renal adjustment
- If a sulfonylurea is indicated for patients with renal impairment, a shorter-acting sulfonylurea like tolbutamide should be prescribed due to particular risk of hypoglycemia.
- Geriatric
- For elderly patients, a shorter-acting sulfonylurea such as tolbutamide should be prescribed due to particular risk of hypoglycemia.
Pharmacokinetics
Duration
Shorter-acting compared to long-acting sulfonylureas like glibenclamide
Half-life
6 hours
Protein binding
Tolbutamide's elimination approaches saturation over the therapeutic range, with kinetics changing from first order to zero order at higher doses.
Metabolism
Tolbutamide is a substrate of CYP2C8/9.
Excretion
Excreted in urine
Contraindications
- Contraindication to sulfonylureas
- Intolerance to sulfonylureas
- pregnancy (change to insulin advised)
- nursing mothers
- liver dysfunction
- kidney dysfunction
Side effects
Common
HypoglycaemiaWeight gainhypoglycaemia (lowest risk among SUs)weight gain (1-3 kg)nauseavomitingflatulencediarrhoeaconstipationheadacheparesthesias
Serious
- Severe hypoglycaemia
- disulfiram-like reaction after alcohol
- rashes
- photosensitivity
- purpura
- transient leukopenia
- agranulocytosis (rare)
Pregnancy & lactation
Lactation
Secreted in milk; should not be given to nursing mothers
Drug interactions
Aminolevulinic Acid
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Cinoxacin
Severe
Database
Drug interaction classified as: antagonism
Source: DDInter
Ciprofloxacin
Severe
Database
Drug interaction classified as: antagonism
Source: DDInter
Delafloxacin
Severe
Database
Clinical effect not specified
Source: DDInter
Enoxacin
Severe
Database
Clinical effect not specified
Source: DDInter
Fluconazole
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Gatifloxacin
Severe
Database
Clinical effect not specified
Source: DDInter
Gemifloxacin
Severe
Database
Clinical effect not specified
Source: DDInter
Grepafloxacin
Severe
Database
Clinical effect not specified
Source: DDInter
Levofloxacin
Severe
Database
Clinical effect not specified
Source: DDInter
Lomefloxacin
Severe
Database
Clinical effect not specified
Source: DDInter
Related guidelines
Other Sulfonylurea drugs
Ask House about Tolbutamide
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Katzung, BNF, Harriet Lane·Verified: 2026-05-10 · House clinical team