lispro

Insulin lispro is created by reversing the positions of lysine and proline at positions B28 and B29 on the insulin B-chain. This structural modification reduces the insulin molecule's tendency to self-associate into hexamers, allowing faster dissociation into monomers after subcutaneous injection, which speeds absorption and onset of action.

Pharmacokinetics: Onset 10-15 minutes, peak effect 1-2 hours, duration 3-4 hours. This profile closely mimics physiologic postprandial insulin release, making it superior to regular insulin for controlling post-meal glucose spikes and reducing risk of delayed hypoglycemia.

Clinical use: Administered subcutaneously immediately before or after meals in both Type 1 and Type 2 diabetes mellitus. Often used in combination with longer-acting basal insulins (e.g., glargine, detemir) as part of basal-bolus regimens, or via insulin pumps for continuous subcutaneous insulin infusion.

Mechanism of action: Like all insulins, lispro binds to insulin receptors (tyrosine kinase receptors) on target cells, promoting glucose uptake into muscle and adipose tissue via GLUT4 translocation, inhibiting hepatic gluconeogenesis and glycogenolysis, and promoting glycogen, protein, and lipid synthesis.

Adverse effects: Primary risk is hypoglycemia, which can present with sweating, tachycardia, confusion, and if severe, seizures or coma. Weight gain and lipodystrophy at injection sites are also possible. Unlike regular insulin, lispro's rapid onset requires careful timing with meals to avoid hypoglycemia if a meal is delayed or skipped.

Other rapid-acting analogs with similar properties include insulin aspart and insulin glulisine. These contrast with long-acting analogs like glargine and detemir, which are engineered for prolonged, steady release.