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First-generation sulfonylurea (short-acting)

Tolbutamide

Tolbutamide is a short-acting first-generation sulfonylurea formerly used to lower blood glucose in type 2 diabetes mellitus. Its relatively short duration of action made it a comparatively lower-risk choice for hypoglycaemia among older sulfonylureas.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It binds to the sulfonylurea receptor on pancreatic beta cells, closing ATP-sensitive potassium channels to cause membrane depolarisation and stimulate endogenous insulin secretion, and therefore requires functioning beta cells to be effective.

Prescribing in practice

  • Like all sulfonylureas it can cause hypoglycaemia, which though generally shorter-lived than with longer-acting agents can still be serious, particularly in the elderly or those with renal or hepatic impairment.
  • It is ineffective in type 1 diabetes and should not be used in diabetic ketoacidosis.
  • Weight gain can occur, and caution is needed in hepatic and renal impairment.

Monitoring

Monitor blood glucose and HbA1c for glycaemic control and remain alert for symptoms of hypoglycaemia, especially in the elderly and those with renal or hepatic impairment.

Counselling the patient

  • Take your dose with or shortly before a meal and do not skip meals.
  • Learn to recognise and treat low blood sugar, such as sweating, shakiness, or confusion.
  • Report episodes of low blood sugar to your clinician.

Evidence & guidelines

Its glucose-lowering action is well established through long-standing historical clinical use, though newer agents are generally now preferred.

Reference: NICE NG28; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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