tolbutamide: clinical use

Prescribing considerations

• Confirm functioning beta-cell type 2 diabetes; tolbutamide is unsuitable for type 1 diabetes or diabetic ketoacidosis.
• Hypoglycaemia susceptibility is increased in older, debilitated or metabolically impaired patients.
• Use caution in mild-to-moderate renal impairment with close glucose monitoring.
• Consider a non-sulfonylurea alternative in G6PD deficiency because haemolytic anaemia can occur.
• Safety and efficacy data are insufficient in children and adolescents.

Contraindications and cautions

• Hypersensitivity to tolbutamide or an excipient
• Current or previous diabetic ketoacidosis
• Insulin-dependent diabetes mellitus
• Serious renal, hepatic, adrenocortical or thyroid impairment
• Unusual physiological stress where insulin is essential, including surgery or pregnancy
• Porphyria
• Breastfeeding

Monitoring

• Monitor blood glucose and longer-term glycaemic control, with additional checks during illness or interacting treatment.
• Assess renal and hepatic function where clinically indicated.
• Check a white-cell count for fever or sore throat and consider platelet assessment for unexplained bruising or bleeding.
• Review recurrent, nocturnal or unrecognised hypoglycaemia promptly.

Clinical pharmacology

Tolbutamide is readily absorbed, highly protein-bound and metabolised hepatically, involving CYP2C9. It is eliminated mainly in urine as metabolites with little glucose-lowering activity; its plasma half-life is generally 4–8 hours but may be longer.

Formulation and product differences

• The selected product is a conventional oral tablet containing 500 mg tolbutamide.
• It is round, white and marked with a scoreline not intended for splitting.
• Excipients include starch, povidone, sodium starch glycollate, magnesium stearate and stearic acid.

Tablet

Route: Oral

Strengths: 500 mg