Which insulin preparation has the longest duration of action and is typically administered once daily for basal insulin coverage?

Explanation

## Long-Acting Insulin Preparations **Key Point:** Insulin glargine is a long-acting basal insulin analog with a duration of 24+ hours, providing consistent background insulin coverage with minimal peak effect. ### Insulin Preparations: Onset, Peak, and Duration | Insulin Type | Onset | Peak | Duration | Frequency | |---|---|---|---|---| | **Rapid-acting (Lispro, Aspart, Glulisine)** | 10–15 min | 1–2 hrs | 4–6 hrs | With meals | | **Regular (Soluble)** | 30 min–1 hr | 2–4 hrs | 6–8 hrs | Before meals | | **NPH (Isophane)** | 1–2 hrs | 4–8 hrs | 12–16 hrs | Once or twice daily | | **Long-acting (Glargine, Detemir, Degludec)** | 1–2 hrs | Minimal/flat | 24+ hrs | Once daily | ### Insulin Glargine (Lantus) 1. **Structure:** Basal insulin analog with glycine at position A21 and two arginines at C-terminus 2. **Pharmacokinetics:** Slow, steady absorption from subcutaneous depot; reaches steady state in 3–4 days 3. **Onset:** 1–2 hours; **Peak:** Relatively flat; **Duration:** 24+ hours 4. **Clinical Use:** Basal insulin in type 1 DM and type 2 DM; provides background glucose control 5. **Advantage:** Once-daily dosing, predictable action, low hypoglycemia risk due to flat profile **High-Yield:** Basal insulins (glargine, detemir, degludec) are designed to mimic the fasting insulin secretion of the pancreas and are NOT meant for mealtime coverage — that role belongs to rapid-acting insulins. **Mnemonic:** **BASAL = Background, Administered once daily, Steady-state, Analog, Long-acting** — remember glargine for basal coverage. **Clinical Pearl:** Insulin glargine should never be mixed with other insulins in the same syringe because its acidic pH (pH 4) causes precipitation with neutral insulins like NPH.