====== Regular Insulin ======

Regular insulin is short-acting human insulin used for prandial control and intravenous insulin therapy.

It has a slower onset and longer duration than rapid-acting insulin analogs.

→ [[endocrine:insulin:start|Insulin Therapy]]

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===== Mechanism of Action =====

Regular insulin binds to the insulin receptor (tyrosine kinase receptor).

This activates:

  * IRS signaling pathways
  * PI3K/Akt cascade
  * GLUT4 translocation in muscle and adipose tissue

Physiologic effects:

Liver:
  * ↓ Gluconeogenesis
  * ↑ Glycogen synthesis

Muscle:
  * ↑ Glucose uptake
  * ↑ Glycogen storage

Adipose:
  * ↑ Glucose uptake
  * ↓ Lipolysis

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===== Pharmacokinetics =====

Regular insulin forms hexamers in solution.

These must dissociate before absorption, which slows onset.

Onset:
  * 30–60 minutes

Peak:
  * 2–4 hours

Duration:
  * 6–8 hours

Compared to:

  * [[endocrine:insulin:lispro|Lispro]]
  * [[endocrine:insulin:aspart|Aspart]]

Regular insulin has:

  * Slower onset
  * Longer duration
  * Greater risk of late hypoglycemia

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===== Clinical Use =====

Subcutaneous use:

  * Mealtime insulin (must be given 30 minutes before eating)

Intravenous use:

  * Diabetic Ketoacidosis (DKA)
  * Hyperosmolar Hyperglycemic State (HHS)
  * Critical care glucose control
  * Severe hyperkalemia (drives potassium intracellularly)

Regular insulin is the insulin used for IV infusion.

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===== DKA Physiology =====

Insulin deficiency leads to:

  * Unchecked lipolysis
  * Ketone production
  * Metabolic acidosis

Treatment:

  * IV [[endocrine:insulin:regular|Regular Insulin]]
  * Fluid resuscitation
  * Potassium monitoring

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===== Adverse Effects =====

  * Hypoglycemia
  * Weight gain
  * Hypokalemia (IV use)

Delayed hypoglycemia risk is higher compared to rapid analogs due to longer duration.

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===== Regular Insulin vs Rapid-Acting Analogs =====

Rapid-acting analogs:

  * [[endocrine:insulin:lispro|Lispro]]
  * [[endocrine:insulin:aspart|Aspart]]
  * [[endocrine:insulin:glulisine|Glulisine]]

Advantages of analogs:

  * Faster onset
  * Shorter duration
  * Less stacking
  * Reduced delayed hypoglycemia

Regular insulin advantages:

  * IV use
  * Lower cost
  * Established inpatient role

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===== Clinical Pearls =====

  * Only insulin used IV
  * Slower onset than rapid analogs
  * Must give 30 minutes before meals
  * Used in DKA and HHS
  * Can cause hypokalemia during IV therapy

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===== Related =====

  * [[endocrine:insulin:start|Insulin Therapy]]
  * [[endocrine:insulin:lispro|Lispro]]
  * [[endocrine:insulin:aspart|Aspart]]
  * [[endocrine:diabetes:start|Diabetes Pharmacology]]