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[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# Sulfonylureas

Oral drugs that make the pancreas release more insulin. Cheap and effective, but the classic cause of drug-induced hypoglycemia.

Updated 2026-11-01

## What they are

Insulin secretagogues for type 2 diabetes. They need working beta cells, so they do not help in type 1 diabetes.

## Mechanism of action

Sulfonylureas bind SUR1, the regulatory subunit of the ATP-sensitive potassium channel (KATP, Kir6.2/SUR1) of the beta cell, and close it. The membrane depolarizes, voltage-gated calcium channels open, calcium enters and insulin granules are released. Because release does not depend on the glucose level, insulin keeps coming even when glucose is already low.

Target: Sulfonylurea receptor 1 (SUR1) of the beta-cell KATP channel

## Key points

- Main adverse effect: hypoglycemia, which can be prolonged and recur; risk is highest in older adults, with kidney or liver failure, missed meals or alcohol.
- They cause weight gain, unlike metformin, SGLT2 inhibitors and GLP-1 agonists.
- Glibenclamide (glyburide) has the highest hypoglycemia risk; gliclazide is preferred on the WHO list.
- They are sulfonamide derivatives and can cause hemolysis in G6PD deficiency.
- Diazoxide does the opposite: it opens the same KATP channel and stops insulin release.

## Drugs in this class

- [**Glibenclamide** A potent, long-acting sulfonylurea: it forces the pancreas to release insulin and carries the highest risk of… Sulfonylurea receptor 1 (SUR1) of the KATP channel](https://durgical.com/en/pharmacology/glibenclamide/)
- [**Gliclazide** The sulfonylurea on the WHO essential list: it raises insulin release with less hypoglycemia than glibenclamide. Sulfonylurea receptor 1 (SUR1) of the KATP channel](https://durgical.com/en/pharmacology/gliclazide/)
- [**Glimepiride** A once-daily sulfonylurea for type 2 diabetes: it increases insulin release and can cause hypoglycemia and weight gain. Sulfonylurea receptor 1 (SUR1) of the KATP channel](https://durgical.com/en/pharmacology/glimepiride/)
- [**Glipizide** A shorter-acting sulfonylurea taken before meals. Its inactive metabolites make it a common choice when kidney… Sulfonylurea receptor 1 (SUR1) of the KATP channel](https://durgical.com/en/pharmacology/glipizide/)

## Others in the class

- tolbutamide (first generation)
- chlorpropamide (first generation, long-acting)

## Test yourself

Think of the answer, then tap the question to see it.

## Why do sulfonylureas not work in type 1 diabetes?

They act by making beta cells release insulin. In type 1 diabetes the beta cells have been destroyed, so there is no insulin to release.

## Which channel do sulfonylureas close, and what happens next in the beta cell?

The ATP-sensitive potassium channel (Kir6.2/SUR1). The cell depolarizes, voltage-gated calcium channels open and the calcium rise triggers insulin release.

## Why can sulfonylurea hypoglycemia return after the patient first recovers?

The drug keeps stimulating insulin release for as long as it is in the body, which is longer in kidney failure or with long-acting agents. Glucose must be watched for many hours.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Glyburide: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a684058.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - GLYBURIDE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a56f100f-0f42-4188-81ab-04644b824040) (DailyMed (U.S. National Library of Medicine), 2026); [Cryo-EM structure of the pancreatic beta-cell KATP channel bound to ATP and glibenclamide](https://www.rcsb.org/structure/6BAA) (RCSB Protein Data Bank, 2017).

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