## Mechanism of Sulfonylureas **Key Point:** Sulfonylureas are insulin secretagogues that work exclusively through stimulation of residual pancreatic beta cell function — they are ineffective when beta cells are absent or non-functional. ### Correct Statements | Feature | Details | |---------|----------| | **Binding site** | ATP-sensitive K⁺ channels (K_ATP) on beta cell membrane | | **Cellular effect** | Block K⁺ efflux → membrane depolarization → Ca²⁺ influx → insulin exocytosis | | **Requirement** | Functional beta cells must be present | | **Glucose dependence** | Stimulate insulin release even in fasting state (risk of hypoglycemia) | ### Why Type 1 Diabetes is NOT Responsive **High-Yield:** Type 1 diabetes involves autoimmune destruction of pancreatic beta cells, resulting in absolute insulin deficiency. Sulfonylureas cannot restore destroyed beta cells and are therefore **contraindicated** in type 1 DM. **Clinical Pearl:** Sulfonylureas are effective only in type 2 DM where residual beta cell function exists. In type 1 DM, insulin replacement is the only option. ### Generations of Sulfonylureas - **First generation** (Tolbutamide, Chlorpropamide): longer half-life, more hypoglycemia risk - **Second generation** (Glibenclamide, Glipizide, Gliclazide): more potent, shorter duration, preferred in current practice **Warning:** Sulfonylureas carry a significant risk of hypoglycemia, especially in elderly patients or those with renal/hepatic impairment. [cite:KD Tripathi 8e Ch 27]
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