Insulin Types: Pharmacokinetics and Clinical Selection

Understanding insulin pharmacokinetics — onset, peak, and duration of each formulation — is essential for NP prescribing to replicate physiological insulin secretion and prevent both hyperglycemia and hypoglycemia. Physiological insulin secretion has two components: basal secretion (continuous low-level insulin release suppressing hepatic glucose output between meals and overnight, approximately 50% of daily insulin production) and bolus/prandial secretion (rapid insulin release in response to meals, peaking within 30-60 minutes of eating, approximately 50% of daily production). Insulin therapy attempts to replicate this physiology using long-acting basal insulins and rapid-acting mealtime insulins. Rapid-acting insulin analogs (lispro, aspart, glulisine) have been engineered through amino acid substitutions that prevent hexamer formation, allowing monomeric absorption from the injection site. Onset 10-15 minutes, peak 1-2 hours, duration 3-5 hours. Inject within 15 minutes of eating. Ultra-rapid formulations (Fiasp — aspart with niacinamide for faster absorption, Lyumjev — lispro with treprostinil and citrate) have onset within 2-5 minutes. These are used for mealtime (bolus) coverage and correction doses. Short-acting (regular) insulin forms hexamers in solution that must dissociate to monomers before absorption. Onset 30 minutes, peak 2-4...