1. Clinical Overview
Insulin Isophane (NPH - Neutral Protamine Hagedorn) is an intermediate-acting insulin suspension used for the management of diabetes mellitus. It is a cloudy, white suspension of human insulin complexed with protamine and zinc, providing a longer duration of action than regular insulin. In India, the 40 IU/mL concentration (U-40) is a legacy strength, though U-100 (100 IU/mL) is now the global standard. U-40 requires specific U-40 syringes for accurate dosing.
| Onset | Duration | Bioavailability |
|---|---|---|
| 1-2 hours | 18-24 hours | Approximately 60-80% (Subcutaneous) |
2. Mechanism of Action
Insulin Isophane is a suspension of insulin complexed with protamine and zinc, which delays absorption from the subcutaneous injection site. Once absorbed, it binds to the insulin receptor, a transmembrane tyrosine kinase receptor, initiating a cascade of intracellular signaling events.
3. Indications & Uses
- Type 1 Diabetes Mellitus (as part of a basal-bolus regimen)
- Type 2 Diabetes Mellitus (when oral agents are insufficient, for basal insulin therapy)
4. Dosage & Administration
Adult Dosage: Highly individualized. Typical starting dose in insulin-naïve Type 2 DM: 0.1-0.2 IU/kg/day, usually administered once daily (at bedtime) or twice daily. Dose is titrated based on fasting blood glucose levels.
Administration: FOR SUBCUTANEOUS USE ONLY. Administer by subcutaneous injection in the abdominal wall, thigh, buttock, or upper arm. Rotate injection sites within the same region to prevent lipodystrophy. Gently roll the vial to resuspend the cloudy suspension; DO NOT SHAKE VIGOROUSLY. Use a U-40 insulin syringe. Inject at a 90-degree angle (or 45 degrees if thin). Typically administered 30-60 minutes before a meal (if used twice daily) or at bedtime (if used once daily).
5. Side Effects
Common side effects may include:
- Hypoglycemia (sweating, tremor, palpitations, hunger)
- Injection site reactions (pain, redness, itching, swelling)
- Lipodystrophy (lipoatrophy or lipohypertrophy at injection sites)
- Weight gain
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Beta-blockers (e.g., Propranolol) | Mask tachycardia warning signs of hypoglycemia; may potentiate or impair glucose recovery. | Major |
| Corticosteroids (e.g., Prednisone) | Increase insulin requirements due to hyperglycemic effect. | Major |
| Thiazide Diuretics (e.g., Hydrochlorothiazide) | May increase blood glucose levels, increasing insulin requirements. | Moderate |
| ACE Inhibitors (e.g., Ramipril) | May enhance hypoglycemic effect. | Moderate |
| Alcohol | Potentiates hypoglycemic effect; can cause delayed hypoglycemia, especially in fasting state. | Major |
| MAO Inhibitors, Anabolic Steroids | Increase hypoglycemic effect. | Moderate |
| Oral Hypoglycemics (e.g., Sulfonylureas) | Additive hypoglycemic effect, increasing hypoglycemia risk. | Major |
7. Patient Counselling
- DO use only U-40 syringes with U-40 insulin.
- DO rotate injection sites within the same body area.
- DO gently roll the vial to mix; do not shake.
- DO check blood glucose levels regularly as advised.
- 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 share needles, pens, or syringes.
8. Toxicology & Storage
Overdose: Profound hypoglycemia: sweating, tremor, tachycardia, anxiety, hunger, confusion, drowsiness, speech disturbance, seizures, loss of consciousness, coma, and death if untreated.
Storage: Unopened vials: Store in a refrigerator at 2°C to 8°C. DO NOT FREEZE. Keep away from the cooling element. In-use vial: Can be kept at room temperature (below 25°C) for up to 28 days. Protect from direct heat and light. Do not use if the suspension clumps, sticks to the vial, or remains cloudy after mixing. Discard any opened vial after 28 days.