1. Clinical Overview
A biphasic isophane insulin injection, also known as biphasic human insulin or 75/25 premixed insulin. It is a sterile suspension containing 75% Insulin Isophane (NPH, an intermediate-acting insulin) and 25% Human Insulin (regular, soluble, short-acting insulin) in a single vial or cartridge. This combination provides both a rapid onset to cover postprandial glucose rise and a prolonged duration to provide basal insulin coverage, simplifying the regimen for patients requiring both meal-time and basal insulin.
| Onset | Duration | Bioavailability |
|---|---|---|
| 30 minutes | Up to 24 hours | Approximately 60-70% (subcutaneous) |
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 (glycogenolysis and gluconeogenesis), and promoting glycogen, lipid, and protein synthesis.
3. Indications & Uses
- Type 2 Diabetes Mellitus (in patients requiring both basal and prandial coverage)
- Type 1 Diabetes Mellitus (as part of a basal-bolus regimen, though less common than analog mixes)
4. Dosage & Administration
Adult Dosage: Highly individualized. Typically initiated at 0.2-0.5 units/kg/day, divided into 2 doses (pre-breakfast and pre-dinner). The total daily dose is often split as 2/3 in the morning and 1/3 in the evening, but must be titrated based on blood glucose monitoring. Usual maintenance range: 0.5-1.0 units/kg/day.
Administration: For SUBCUTANEOUS injection only. Administer 30-45 minutes before a meal. Rotate injection sites (abdomen, thigh, buttocks, upper arm) to prevent lipodystrophy. Gently roll the vial/pen to resuspend; do not shake. Inspect visually; it should be uniformly cloudy/milky. Do not use if clear, discolored, or contains particles. Use appropriate insulin syringe (U-100) or delivery device.
5. Side Effects
Common side effects may include:
- Hypoglycemia (most common)
- Injection site reactions (pain, redness, itching, swelling)
- Lipodystrophy (lipoatrophy or lipohypertrophy at injection sites)
- Weight gain
- Peripheral edema (especially upon initiation)
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, requiring dose increase. | Major |
| Beta-blockers (e.g., Propranolol) | May mask tachycardia symptoms of hypoglycemia, potentiate hypoglycemia, and impair recovery. | Moderate |
| Thiazide Diuretics (e.g., Hydrochlorothiazide) | May cause hyperglycemia, increasing insulin requirements. | Moderate |
| ACE Inhibitors (e.g., Ramipril) | May enhance insulin sensitivity, increasing hypoglycemia risk. | Moderate |
| Alcohol | Potentiates hypoglycemic effect and can cause delayed hypoglycemia, especially in fasting state. | Major |
| MAO Inhibitors, Anabolic Steroids | Increase hypoglycemic effect. | Moderate |
| Thyroid Hormones, Somatropin, Danazol | Increase blood glucose, requiring higher insulin doses. | Moderate |
7. Patient Counselling
- DO check blood sugar levels regularly as advised by your doctor.
- DO inject 30-45 minutes BEFORE your main meals (breakfast and dinner).
- DO rotate injection sites systematically to prevent skin problems.
- DO gently roll the vial/pen to mix before each injection. DO NOT SHAKE.
- DO carry a fast-acting sugar source (glucose tablets) at all times.
- DO wear a diabetes identification bracelet/necklace.
- DON'T change the brand or type of insulin without consulting your doctor.
- DON'T inject into moles, scars, or areas of lipodystrophy.
- DON'T skip or delay meals after injecting insulin.
- DON'T drink alcohol without eating food.
8. Toxicology & Storage
Overdose: Symptoms are those of profound HYPOGLYCEMIA: Mild: Sweating, palpitations, tremor, hunger, anxiety. Moderate: Confusion, drowsiness, slurred speech, behavioral changes. Severe: Seizures, loss of consciousness, coma, neurological damage, death.
Storage: Unopened (Refrigerated): Store between 2°C to 8°C in a refrigerator. DO NOT FREEZE. Keep away from freezer compartment and direct sunlight. In Use (Room Temperature): Once in use, the vial can be kept at room temperature (below 30°C) for up to 4 weeks. The pen-in-use can be kept at room temperature for up to 4 weeks. Protect from excessive heat and light. Do not use if it has been frozen, discolored, or contains clumps or particles after proper mixing. Discard any remaining insulin after the recommended in-use period.