1. Clinical Overview
A biphasic isophane insulin injection, also known as biphasic human insulin or 50/50 mixed insulin. It is a sterile, white, and cloudy suspension containing 50% intermediate-acting Insulin Isophane (NPH) and 50% short-acting Human Insulin (Soluble/Regular Insulin) in a neutral phosphate buffer. This premixed formulation is designed to provide both prandial (mealtime) and basal (background) insulin coverage in a single injection, simplifying the regimen for patients with diabetes mellitus. It is a critical component of diabetes management in the Indian healthcare setting due to its cost-effectiveness and ease of use.
| Onset | Duration | Bioavailability |
|---|---|---|
| 30 minutes | Up to 24 hours (Peak effect: 2-12 hours) | Approximately 60-70% via subcutaneous route |
2. Mechanism of Action
Insulin is the principal hormone required for proper glucose utilization. It regulates carbohydrate, lipid, and protein metabolism by promoting cellular uptake of glucose (especially in muscle and adipose tissue), inhibiting hepatic glucose production (gluconeogenesis and glycogenolysis), and promoting glycogen, lipid, and protein synthesis. The soluble insulin component acts rapidly to control postprandial glucose rises, while the isophane (NPH) component provides a prolonged action to manage interprandial and basal glucose levels.
3. Indications & Uses
- Type 1 Diabetes Mellitus (insulin-dependent)
- Type 2 Diabetes Mellitus (when oral antidiabetic drugs are insufficient or contraindicated)
- Gestational Diabetes Mellitus (when medical nutrition therapy fails)
4. Dosage & Administration
Adult Dosage: Highly individualized. Typically administered once or twice daily (before breakfast and/or before dinner). Starting dose in insulin-naïve patients: 0.2-0.4 units/kg/day, divided. Often given 15-30 minutes before a major meal. Dose adjusted based on self-monitored blood glucose (SMBG) patterns.
Administration: For subcutaneous use ONLY. Inject into abdominal wall, thigh, buttocks, or upper arm. Rotate sites within a region to prevent lipodystrophy. Use a U-100 insulin syringe or pen device. Before use, resuspend gently by rolling between palms until uniformly cloudy. Do not use if clear droplets remain or if clumping/frosting occurs. Do not mix with other insulins in the same syringe (as it is already premixed). Administer 15-30 minutes before a meal.
5. Side Effects
Common side effects may include:
- Hypoglycemia (most common and serious)
- Injection site reactions (pain, redness, itching, swelling)
- Lipodystrophy (lipohypertrophy or lipoatrophy at injection sites)
- Weight gain
- Peripheral edema (especially upon initiation or intensification)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Oral Hypoglycemic Agents (Sulfonylureas, Meglitinides) | Additive hypoglycemic effect, increased risk of hypoglycemia | Major |
| Corticosteroids (e.g., Prednisolone, Dexamethasone) | Antagonize insulin effect, cause hyperglycemia, increased insulin requirement | Major |
| Beta-blockers (e.g., Propranolol) | May mask tachycardia of hypoglycemia, potentiate hypoglycemia, impair recovery | Moderate |
| Thiazide Diuretics (e.g., Hydrochlorothiazide) | Cause hyperglycemia, increased insulin requirement | Moderate |
| Alcohol | Potentiates hypoglycemic effect, risk of delayed hypoglycemia, especially overnight | Major |
| ACE Inhibitors (e.g., Ramipril), MAOIs, Pentamidine | May increase hypoglycemic effect | Moderate |
| Thyroid hormones, Somatropin, Danazol | May increase insulin requirement | Moderate |
7. Patient Counselling
- DO check blood sugar levels regularly as advised.
- DO inject subcutaneously, rotating sites within an area.
- DO resuspend the insulin gently until uniformly cloudy before each use.
- DO administer 15-30 minutes before a meal.
- DO carry a quick sugar source (glucose tablets) at all times.
- DO wear a diabetic identification bracelet.
- DON'T shake the vial/pen vigorously.
- DON'T inject into muscle or a vein.
- DON'T use if the insulin appears clear or has clumps.
- DON'T skip meals after injection.
- DON'T drink alcohol without precautions.
8. Toxicology & Storage
Overdose: Symptoms are those of hypoglycemia: Mild: Hunger, sweating, paresthesia, tachycardia, palpitations. Moderate: Cognitive impairment, confusion, drowsiness, speech difficulty. Severe: Seizures, coma, permanent brain damage, death.
Storage: Unopened vials/pens: Store in a refrigerator at 2°C to 8°C. Do not freeze. Keep away from the freezer compartment and direct heat/light. Opened (in-use) vial: Can be kept at room temperature (below 25°C) or refrigerated for up to 4 weeks. Opened (in-use) pen: Can be kept at room temperature (below 25°C) for up to 4 weeks. Do not store with needle attached. Protect from excessive heat and sunlight. Do not use if frozen, discolored, or precipitated.