Usage
- Insulin isophane is prescribed for type 1 and type 2 diabetes mellitus to control blood sugar levels.
- Pharmacological classification: Intermediate-acting insulin, antidiabetic agent.
- Mechanism of action: Mimics the action of endogenous insulin, facilitating glucose uptake into cells from the bloodstream, thus lowering blood glucose levels.
Alternate Names
- NPH insulin
- Isophane insulin
- Brand names: Humulin N, Novolin N, Insulatard
How It Works
-
Pharmacodynamics: Lowers blood glucose by increasing glucose uptake into muscle, liver, and fat cells; suppresses hepatic glucose production and promotes glycogen synthesis.
-
Pharmacokinetics:
- Absorption: Subcutaneous injection; slower onset and longer duration of action compared to regular insulin. Peak effect occurs 4-12 hours after injection, with a duration of action up to 24 hours. Absorption rate can vary depending on injection site, blood flow, and physical activity.
- Metabolism: Primarily degraded by insulin-degrading enzyme in liver, kidney, and muscle.
- Elimination: Renal excretion of metabolites.
-
Mode of action: Binds to insulin receptors on cell surfaces, triggering intracellular signaling pathways leading to increased glucose transport via GLUT4 transporters and other metabolic effects.
Dosage
Standard Dosage
Adults:
- Initial dose is individualized based on blood glucose levels and metabolic needs, typically starting at 0.1-0.2 units/kg/day, or 10 units/day. The total daily dose is usually split, with 2/3 administered in the morning and 1/3 in the evening.
- Dose adjustments are made based on self-monitored blood glucose (SMBG) levels; increased by 2-4 units or 10-15% one or twice weekly until target blood glucose levels are reached.
Children:
- Pediatric dosage: 0.5-1 unit/kg/day, adjusted based on SMBG.
- Dosage adjustments are made based on SMBG until target blood glucose is achieved.
Special Cases:
- Elderly patients: Start with lower doses and titrate carefully due to potential decreased renal function and increased risk of hypoglycemia.
- Patients with renal impairment: Dose reduction may be necessary.
- Patients with hepatic dysfunction: Dose adjustment may be required.
- Patients with comorbid conditions: Careful monitoring and dose adjustment based on metabolic needs.
Clinical Use Cases
Insulin isophane is typically used for management of diabetes as part of a basal-bolus regimen or as a twice daily injection. Dosage and regimen adjustments are patient-specific and based on their individual needs and medical history. Its use in clinical settings such as intubation, surgical procedures, mechanical ventilation, ICU use, and emergency situations (where tighter and more complex glycemic control is usually required) is less common than rapid-acting or short-acting insulins because of its prolonged action and less predictable behavior.
Dosage Adjustments
- Dose modification according to renal/hepatic function, concurrent medications, and other individual factors as assessed by the physician.
Side Effects
Common Side Effects
- Hypoglycemia (low blood sugar)
- Injection site reactions (redness, swelling, itching)
- Weight gain
Rare but Serious Side Effects
- Severe hypoglycemia (loss of consciousness, seizures)
- Allergic reactions (rash, hives, difficulty breathing, swelling of face/throat)
- Hypokalemia (low potassium)
Long-Term Effects
- Lipodystrophy (changes in skin thickness at injection site)
Adverse Drug Reactions (ADR)
Contraindications
- Hypoglycemia
- Hypersensitivity to insulin isophane or any of its components
Drug Interactions
- Alcohol, beta-blockers, ACE inhibitors, and salicylates can potentiate the hypoglycemic effect of insulin.
- Corticosteroids, thiazide diuretics, and atypical antipsychotics may increase insulin resistance, requiring dose adjustments.
- Many other drugs may interact; thorough medication review needed.
Pregnancy and Breastfeeding
- Pregnancy: Insulin isophane is generally considered safe during pregnancy; dose adjustments may be necessary.
- Breastfeeding: Compatible with breastfeeding; insulin does not pass into breastmilk in clinically significant amounts.
Drug Profile Summary
- Mechanism of Action: Enhances glucose uptake into cells and inhibits hepatic glucose production.
- Side Effects: Hypoglycemia, injection site reactions, weight gain.
- Contraindications: Hypoglycemia, hypersensitivity.
- Drug Interactions: Numerous drug interactions, including alcohol, beta-blockers, ACE inhibitors.
- Pregnancy & Breastfeeding: Generally safe.
- Dosage: Individualized based on blood glucose, starting at 0.1-0.2 units/kg/day.
- Monitoring Parameters: Blood glucose levels, HbA1c.
Popular Combinations
- Often combined with rapid-acting or short-acting insulin to provide both basal and bolus insulin coverage (basal-bolus regimen). Also available as a pre-mixed formulation containing both NPH and regular human insulins (e.g. Humulin 70/30).
Precautions
- Monitor blood glucose regularly.
- Adjust dose as needed during illness, stress, or changes in physical activity.
- Educate patients about signs and symptoms of hypoglycemia and its management.
- Rotate injection sites.
- Screen for allergies.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Insulin Isophane?
A: Starting dose is 0.1-0.2 unit/kg/day or 10 units/day, adjusted based on patient response and glucose monitoring; pediatric dosage 0.5-1 unit/kg/day.
Q2: How is Insulin Isophane administered?
A: Subcutaneous injection, typically once or twice daily.
Q3: What are the common side effects of Insulin Isophane?
A: Hypoglycemia, injection site reactions, and weight gain.
Q4: What are the signs of hypoglycemia?
A: Tremors, sweating, anxiety, confusion, dizziness, palpitations, and hunger.
Q5: What should a patient do if they experience hypoglycemia?
A: Consume fast-acting carbohydrates (e.g., glucose tablets, fruit juice) or administer glucagon if severe.
Q6: Can Insulin Isophane be used during pregnancy?
A: Yes, it is generally considered safe; dose adjustments are usually needed.
Q7: Does Insulin Isophane interact with other medications?
A: Yes, numerous drug interactions; a comprehensive medication review is essential.
Q8: How should Insulin Isophane be stored?
A: Unopened vials should be refrigerated; in-use vials can be stored at room temperature for up to 31 days away from direct sunlight and heat. Do not freeze.
Q9: What is the difference between insulin isophane and regular insulin?
A: Insulin isophane is intermediate-acting, with a slower onset and longer duration of action compared to regular insulin, which is short-acting.
Q10: How often should injection sites be rotated?
A: Rotate injection sites within the same anatomical area (e.g., abdomen) every 1-2 weeks to minimize the risk of lipodystrophy.
