1. Clinical Overview
Insulin glargine is a long-acting, recombinant human insulin analogue used to manage hyperglycemia in diabetes mellitus. It is produced by DNA recombinant technology utilizing a non-pathogenic laboratory strain of Escherichia coli (K12). It differs from human insulin by the replacement of asparagine at position A21 with glycine and the addition of two arginine molecules to the C-terminus of the B-chain. This modification shifts the isoelectric point, making it less soluble at physiological pH, resulting in a slow, prolonged, and peakless absorption profile after subcutaneous injection, providing basal insulin coverage for approximately 24 hours.
| Onset | Duration | Bioavailability |
|---|---|---|
| 2-4 hours | Up to 24 hours (or longer in some individuals) | Approximately 60-70% after subcutaneous administration |
2. Mechanism of Action
Insulin glargine binds to the insulin receptor on target cells (primarily liver, muscle, and adipose tissue), initiating a cascade of intracellular signaling events. This leads to increased cellular uptake of glucose (especially in muscle and fat), inhibition of hepatic glucose production (glycogenolysis and gluconeogenesis), and promotion of glycogen, protein, and lipid synthesis.
3. Indications & Uses
- Type 1 Diabetes Mellitus (for basal insulin requirement)
- Type 2 Diabetes Mellitus (for basal insulin requirement when oral anti-diabetic drugs are insufficient)
4. Dosage & Administration
Adult Dosage: Individualized. Typically initiated at 0.2-0.4 IU/kg/day or 10 IU once daily, adjusted based on fasting blood glucose (FBG) targets. Dose is titrated upwards by 2-4 IU every 3-4 days until FBG target is achieved.
Administration: For subcutaneous injection only. Administer once daily at the same time every day, preferably at bedtime. Rotate injection sites (abdomen, thigh, or upper arm) to prevent lipodystrophy. Inject into the subcutaneous tissue, not intramuscularly. Use a new needle for each injection. Do not shake the vial/cartridge. Inspect visually for clarity before use.
5. Side Effects
Common side effects may include:
- Hypoglycemia (most common)
- Injection site reactions (pain, redness, itching, swelling)
- Lipodystrophy (atrophy or hypertrophy at injection site)
- Peripheral edema
- Weight gain
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Oral Hypoglycemic Agents (e.g., Sulfonylureas, Meglitinides) | Additive hypoglycemic effect, increased risk of hypoglycemia. | Major |
| Corticosteroids (e.g., Prednisolone, Dexamethasone) | Antagonize insulin effect, leading to hyperglycemia and increased insulin requirement. | Major |
| Beta-blockers (e.g., Propranolol, Atenolol) | May mask tachycardia (a warning sign of hypoglycemia) and impair counter-regulatory response. | Moderate |
| Thiazide Diuretics (e.g., Hydrochlorothiazide) | May cause hyperglycemia, increasing insulin requirement. | Moderate |
| ACE Inhibitors (e.g., Ramipril) | May enhance insulin sensitivity, increasing hypoglycemia risk. | Moderate |
| Alcohol | Potentiates hypoglycemic effect and impairs gluconeogenesis. Risk of delayed hypoglycemia. | Major |
| MAO Inhibitors, Anabolic Steroids | Increase hypoglycemic effect. | Moderate |
7. Patient Counselling
- DO inject subcutaneously, rotating sites.
- DO use a new sterile needle for each injection.
- DO monitor blood glucose regularly, especially fasting levels.
- DO keep a regular schedule for meals and injections.
- DON'T mix insulin glargine with any other insulin in the same syringe.
- DON'T shake the vial/cartridge vigorously.
- DON'T inject into muscle, scar tissue, or areas of lipodystrophy.
- DON'T skip doses.
8. Toxicology & Storage
Overdose: Profound hypoglycemia: sweating, palpitations, tremor, anxiety, hunger, confusion, drowsiness, speech difficulty, headache, seizures, coma, and potentially death.
Storage: Unopened (Refrigerated): Store at 2°C to 8°C. Do not freeze. Keep away from direct heat and light. In-use (Opened): Vial/Cartridge/Pen in use can be kept at room temperature (below 30°C) for up to 28 days. Do not refrigerate the product in use. Protect from excessive heat and sunlight. Discard after 28 days, even if solution remains. Do not use if cloudy, discolored, or contains particles.