1. Clinical Overview
Insulin Lispro is a rapid-acting human insulin analogue used for the management of hyperglycemia in diabetes mellitus. It is created by reversing the amino acids proline and lysine at positions 28 and 29 of the human insulin B-chain. This modification reduces the propensity for self-association into dimers and hexamers, allowing for faster absorption from subcutaneous tissue, a more rapid onset of action, and a shorter duration of effect compared to regular human insulin. It is typically administered immediately before or after meals to control postprandial glucose excursions.
| Onset | Duration | Bioavailability |
|---|---|---|
| Approximately 15 minutes after subcutaneous injection. | Approximately 2 to 5 hours. | 55-77% after subcutaneous administration. |
2. Mechanism of Action
Insulin Lispro binds to the alpha-subunit of the transmembrane insulin receptor, a tyrosine kinase receptor, on target cells (primarily liver, muscle, and adipose tissue). This binding triggers autophosphorylation of the receptor and subsequent phosphorylation of intracellular signaling proteins (IRS-1, Shc). This activates two main pathways: the PI3-kinase/Akt pathway (mediating metabolic effects like glucose uptake and glycogen synthesis) and the MAP-kinase pathway (mediating growth-promoting effects).
3. Indications & Uses
- Management of Type 1 Diabetes Mellitus
- Management of Type 2 Diabetes Mellitus in patients requiring insulin therapy
4. Dosage & Administration
Adult Dosage: Highly individualized. Typically 0.5 to 1.0 unit/kg/day, divided into multiple doses. The pre-meal dose is based on carbohydrate intake, pre-meal blood glucose, and anticipated physical activity. Usually administered 0-15 minutes before or immediately after a meal.
Administration: For subcutaneous use only. Inject into abdominal wall, thigh, buttocks, or upper arm. Rotate injection sites within the same region. Use a new needle for each injection. Do not mix with other insulins in the same syringe unless specifically indicated (e.g., with specific NPH formulations). If using a pre-filled pen, prime the needle with 2 units before each injection. Do not share pens or needles.
5. Side Effects
Common side effects may include:
- Hypoglycemia (sweating, tremor, palpitations, hunger, confusion)
- Injection site reactions (redness, swelling, itching, lipodystrophy)
- Weight gain
- Peripheral edema
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Corticosteroids (e.g., Prednisolone) | Antagonize insulin effect, increasing blood glucose. Requires dose increase. | Major |
| Beta-blockers (e.g., Propranolol) | May mask tachycardia of hypoglycemia and impair counter-regulatory response. Can also potentiate hypoglycemic effect. | Moderate |
| Thiazolidinediones (e.g., Pioglitazone) | Can cause fluid retention, exacerbating or precipitating heart failure. Monitor weight and edema. | Major |
| Alcohol | Potentiates hypoglycemic effect and impairs gluconeogenesis. Risk of delayed hypoglycemia. | Major |
| MAO Inhibitors, ACE Inhibitors | May potentiate hypoglycemic effect. | Moderate |
| Oral Hypoglycemics (Sulfonylureas, Meglitinides) | Additive hypoglycemic effect. Risk of severe hypoglycemia. | Major |
| Thyroid Hormones, Diuretics (Thiazides, Loop) | May increase blood glucose, requiring insulin dose adjustment. | Moderate |
7. Patient Counselling
- DO check blood sugar levels regularly, especially before meals, driving, and exercise.
- DO inject 0-15 minutes before or immediately after starting a meal.
- DO rotate injection sites within the same body area to prevent lipodystrophy.
- DO carry a fast-acting sugar source (glucose tablets) and a glucagon kit at all times.
- DO store unopened vials/pens in a refrigerator (2-8°C). Do not freeze.
- DON'T share pens, needles, or syringes.
- DON'T inject into moles, scars, or areas of lipodystrophy.
- DON'T skip or delay meals after injection.
- DON'T use if the solution is cloudy, discolored, or contains particles.
8. Toxicology & Storage
Overdose: Symptoms are those of hypoglycemia: Mild (sweating, palpitations, hunger), Moderate (confusion, drowsiness, slurred speech), Severe (seizures, unconsciousness, coma, neurological damage, death).
Storage: Unopened (Not in Use): Store in a refrigerator at 2°C to 8°C. Do not freeze. Keep away from the cooling element. In Use (Opened Vial/Pen): Can be kept at room temperature (below 30°C) for up to 28 days. Protect from direct heat and light. Do not refrigerate the pen in use. Discard after 28 days, even if solution remains. Do not use if frozen or exposed to temperatures >30°C. Keep out of reach of children.