A 32-year-old woman presents with polyuria, polydipsia, and weight loss for 3 weeks. Blood glucose is 380 mg/dL, pH 7.28, HCO₃⁻ 12 mEq/L, and C-peptide is undetectable. She is diagnosed with Type 1 diabetes mellitus presenting with diabetic ketoacidosis. After acute management and stabilization, what is the drug of choice for long-term glycemic control?

Explanation

## Pathophysiology of Type 1 Diabetes **Key Point:** Type 1 diabetes is an autoimmune destruction of pancreatic β-cells resulting in absolute insulin deficiency. Patients cannot produce endogenous insulin and are insulin-dependent for survival. ## Why Insulin Is the Drug of Choice ### Mechanism 1. Absolute insulin deficiency requires exogenous insulin replacement 2. No functional β-cells remain to respond to oral hypoglycemic agents 3. Insulin restores glucose homeostasis and prevents ketoacidosis ### Insulin Regimen in Type 1 Diabetes | Insulin Type | Onset | Peak | Duration | Role in Type 1 | |---|---|---|---|---| | **Basal (Glargine/Detemir)** | 1–2 hrs | Minimal | 24 hrs | Once/twice daily long-acting | | **Bolus (Rapid-acting: Aspart/Lispro)** | 10–15 min | 1–2 hrs | 4–6 hrs | With meals | | **NPH (Intermediate)** | 2–4 hrs | 6–10 hrs | 12–18 hrs | Older alternative | **High-Yield:** The standard regimen is **basal-bolus**: a long-acting insulin (glargine, detemir) once or twice daily plus rapid-acting insulin before meals. Glargine is preferred as first-line basal insulin due to once-daily dosing and lower hypoglycemia risk. **Clinical Pearl:** Insulin is the ONLY drug that can replace absolute insulin deficiency. Oral agents (metformin, sulfonylureas, thiazolidinediones) require residual β-cell function and are ineffective in Type 1 diabetes. **Key Point:** Undetectable C-peptide confirms absent endogenous insulin production—a hallmark of Type 1 diabetes requiring lifelong insulin therapy. ## Why Other Drugs Fail - **Metformin**: Improves insulin sensitivity but cannot replace absent insulin - **Sulfonylureas (Glibenclamide)**: Stimulate remaining β-cells—ineffective when β-cells are destroyed - **Thiazolidinediones (Pioglitazone)**: Enhance insulin action peripherally but do not provide insulin itself [cite:Harrison 21e Ch 417]