3. Sulphonylureas
• Lower blood glucose in normal persons and
type 2 diabetics
• Not effective in type 1 diabetics
PgBlazer.com
4. Mechanism of action – Sulphonylureas
SUR1 receptors on pancreatic β cell membrane
Binding to receptor
Reduced conductance of ATP sensitive K+ channels
Depolarization of membrane
Enhanced Ca2+ influx
Degranulation of insulin vesicles
PgBlazer.com
5. Mechanism of action – Sulphonylureas
• Augment 2nd phase of insulin secretion
• At least 30% functional β cells required
PgBlazer.com
6. Extrapancreatic action – Sulphonylureas
• Chronic administration – downregulation of
sulphonylurea receptors
– Insulin release decreased
• But control of blood sugar is maintained
• Tissues are sensitized to insulin
– By Increase in insulin receptors and/or
postreceptor action
PgBlazer.com
7. Pharmacokinetics – Sulphonylureas
• Well absorbed orally
• High plasma protein binding – 90%
• Low volume of distribution – 0.2-0.4 L/kg
PgBlazer.com
14. Adverse Effects – Sulphonylureas
• Hypoglycemia
– Commonest
– More in elderly, liver+kidney disease
– More with Chlorpropamide – long action
– Least with Tolbutamide – low potency, short
action
• Non specific side effects
• Hypersensitivity
PgBlazer.com
15. Adverse Effects – Sulphonylureas
• Hypoglycemia
• Non specific side effects
– Nausea
– Vomiting
– Flatulence
– Diarrhoea/constipation
– Headache
– Paresthesias
– Weight gain
• Hypersensitivity
PgBlazer.com
16. Adverse Effects – Sulphonylureas
• Hypoglycemia
• Non specific side effects
• Hypersensitivity
– Rashes
– Photosensitivity
– Prupura
– Transient leukopenia
– Agranulocytosis (rare)
PgBlazer.com
17. Adverse Effects – Sulphonylureas
• Chlorpropamide
– Cholestatic jaundice
– Dilutional hyponatremia (sensitise kidney to ADH)
– Disulfuram like reactions
• Tolbutamide
– Reduce iodine uptake by thyroid
• Does not cause hypothyroidism
• Should changeover to insulin during
pregnancy
PgBlazer.com