1. Clinical Overview
Insulin glargine is a long-acting, recombinant human insulin analogue used for the control of hyperglycemia in diabetes mellitus. It is a clear, colourless solution for subcutaneous injection. The 3.64 IU/ml concentration is equivalent to 100 IU/ml (U-100) in terms of biological activity, but presented in a 1:1.5 ratio (3.64 IU/ml = 100 IU/1.5ml) for specific pen devices. It is designed to provide a basal level of insulin with a relatively constant concentration/time profile over 24 hours with a single daily injection.
| Onset | Duration | Bioavailability |
|---|---|---|
| 1-2 hours | Up to 24 hours (mean duration approximately 22 hours) | Approximately 60-70% following subcutaneous administration |
2. Mechanism of Action
Insulin glargine is a human insulin analogue where asparagine at position A21 is replaced by glycine and two arginines are added to the C-terminus of the B-chain. This modification shifts the isoelectric point towards a neutral pH, making it less soluble at physiological pH. After subcutaneous injection, it forms microprecipitates from which small amounts of insulin glargine are slowly released, resulting in a prolonged, relatively peakless profile.
3. Indications & Uses
- Type 1 Diabetes Mellitus (as basal insulin)
- Type 2 Diabetes Mellitus (as basal insulin, when oral agents are insufficient)
4. Dosage & Administration
Adult Dosage: Individualized. Typically initiated at 0.2 IU/kg or 10 IU once daily, adjusted based on fasting blood glucose (FBG) targets. Dose is titrated 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 each day, preferably at bedtime. Rotate injection sites (abdomen, thigh, upper arm) to prevent lipodystrophy. Use a new needle for each injection. Do not shake. Inspect visually; should be clear and colourless. Do not administer intravenously or intramuscularly.
5. Side Effects
Common side effects may include:
- Hypoglycemia
- Injection site reactions (pain, redness, itching)
- Lipodystrophy (atrophy or hypertrophy at injection site)
- Peripheral edema
- Weight gain
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Oral Hypoglycemics (Sulfonylureas, Meglitinides) | Additive hypoglycemic effect | Major |
| Beta-blockers (e.g., Propranolol) | Mask tachycardia warning signs of hypoglycemia; may potentiate or impair glucose recovery | Moderate |
| Thiazides, Loop Diuretics | May cause hyperglycemia, increasing insulin requirement | Moderate |
| Corticosteroids (e.g., Prednisolone) | Cause hyperglycemia, increasing insulin requirement | Major |
| ACE Inhibitors, MAOIs, Pentamidine | May increase hypoglycemic effect | Moderate |
| Alcohol | Potentiates hypoglycemic effect; can cause delayed hypoglycemia | Major |
7. Patient Counselling
- DO inject subcutaneously at a 90-degree angle using a proper technique.
- DO rotate injection sites systematically.
- DO check blood glucose levels regularly as advised.
- DO carry a fast-acting sugar source (glucose tablets) at all times.
- DO keep spare insulin and supplies.
- DON'T mix insulin glargine with any other insulin in the same syringe.
- DON'T share needles or pens.
- DON'T skip meals after injection.
- DON'T use if solution is cloudy, discolored, or contains particles.
8. Toxicology & Storage
Overdose: Profound hypoglycemia: sweating, pallor, tremor, anxiety, palpitations, hunger, confusion, drowsiness, speech difficulty, headache, seizures, coma, and death.
Storage: Unopened (Refrigerated): Store at 2°C to 8°C. Do not freeze. Keep away from freezer compartment and direct sunlight. Opened/In-use: Can be stored at room temperature (below 25°C) for up to 28 days. Do not refrigerate the pen in use. Protect from excessive heat and light. Discard after 28 days, even if some solution remains. Do not use if frozen or exposed to temperatures >30°C.