💊 Sulfonylureas
Drug Class & Overview
Sulfonylureas are oral antihyperglycaemic agents used in the management of Type 2 Diabetes Mellitus, typically as a second-line agent when metformin is contraindicated or not tolerated, or in combination therapy.
Mechanism of Action
Sulfonylureas stimulate insulin secretion from the pancreatic beta cells by binding to and blocking ATP-sensitive potassium channels. This depolarises the beta cell membrane, opening voltage-gated calcium channels, leading to an influx of calcium and subsequent insulin release.
Key Indications
Sulfonylureas are indicated for Type 2 Diabetes Mellitus when diet and exercise alone are insufficient, and metformin is not appropriate or tolerated. They are often used in combination with metformin or other oral agents, or as monotherapy in patients who are not overweight.
Contraindications
Contraindications include Type 1 Diabetes Mellitus, diabetic ketoacidosis, severe renal or hepatic impairment, and pregnancy/breastfeeding. They should be used with caution in elderly patients due to an increased risk of hypoglycaemia.
Adverse Effects
The most significant adverse effect is hypoglycaemia, which can be severe and prolonged. Other common side effects include weight gain, gastrointestinal disturbances (nausea, vomiting), and hypersensitivity reactions (rash). Rarely, bone marrow suppression has been reported.
Monitoring
Regular monitoring of blood glucose levels is essential to prevent and detect hypoglycaemia. HbA1c is monitored every 3-6 months to assess long-term glycaemic control. Renal and hepatic function should be monitored periodically, especially in elderly patients.
Prescribing Safety (OSCE)
When prescribing sulfonylureas, always check for renal and hepatic impairment, as these increase the risk of hypoglycaemia. Counsel patients thoroughly on the symptoms and management of hypoglycaemia, and the importance of regular meals. Be aware of potential interactions with drugs that can potentiate hypoglycaemia (e.g., alcohol, NSAIDs).
MLA High-Yield Notes
Sulfonylureas are effective at lowering blood glucose but carry a significant risk of hypoglycaemia and weight gain. Gliclazide is a commonly used sulfonylurea in the UK due to a lower risk of hypoglycaemia compared to older agents. Remember they are not suitable for Type 1 Diabetes.
Common SBA Themes
SBAs often test the mechanism of action (insulin secretagogue) and the primary adverse effect (hypoglycaemia). Questions may also focus on their place in therapy (second-line after metformin) and contraindications, particularly in Type 1 Diabetes.
References
- BNF (British National Formulary)
- NICE Guideline NG28: Type 2 diabetes in adults: management
- MHRA Drug Safety Update: Sulfonylureas and risk of hypoglycaemia