Insulin Replacement

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Insulin Replacement

• Insulin is necessary for all cases of Type I DM.

• (It is used in some Type II patients: ~30% within 15 years of diagnosis).

Classifications

• Source

  • Semi-synthetic human sequence insulin, 

  • Porcine insulin, 

  • (Beef insulin is rarely used).

• Duration of action

  • Soluble, 

  • Isophane, 

  • Lente, 

  • Analogues.

Aim

To supplement or replace the patient’s natural insulin.

Mechanism of Action

• See Insulin 

Pharmacokinetics.

• short-acting insulin (soluble insulin, insulin lispro, insulin aspart)
  • onset 30-60 mins
  • max effect 2-4 hours
  • duration ~8 hours
• intermediate-acting insulin (isophane insulin, insulin zinc suspension)
  • onset 1-2 hours
  • max effect 4-8 hours
  • duration 16-35 hours
• long-acting insulin (crystalline insulin zinc suspension)

Routine maintenance.

• Proportions of 2/3 intermediate-acting and 1/3 short-acting given sub-cutaneously.
• (Increase short-acting proportion if patient has excessive post-prandial hyperglycaemia.)
• Usually 50-70% given before breakfast, 30-50% before evening meal.

Emergencies.

• e.g. in ketoacidosis, labour, surgery, vomiting.
• Short-acting insulin given intravenously.
• (n.b. only short-acting can be given i/v.)

 Examples of recommended insulin regimens (BNF).

• Example 1
  • Short-acting mixed with intermediate-acting insulin – 2x day before meals
• Example 2
  • Short-acting mixed with intermediate-acting insulin – before breakfast.
  • Short-acting insulin – before evening meal
  • Intermediate-acting insulin – at bedtime.
• Example 3
  • Short-acting insulin – 3x day before breakfast, lunch and evening meal.
  • Intermediate-acting insulin – at bedtime.
• Example 4
  • Intermediate-acting insulin with or without short-acting insulin – before breakfast or on its own at bedtime (some Type II patients).
• Example 5
  • For the best possible control with the lowest risk of hypoglycaemia, a continuous s/c infusion of Humalogue with pre-prandial boosts can be given with a portable infusion pump

Changing Requirements

Patients have increased requirements in:

• infection
• stress
• accidental / surgical trauma
• puberty
• 2^nd and 3^rd trimesters of pregnancy

Patients have decreased requirements in

• renal / hepatic impairment
• some endocrine disorders (e.g. Addison’s, hypopituitism)
• coeliac disease

Patients’ requirements must be assessed often in:

• pregnancy

Side Effects

• Hypoglycaemia
• Insulin-induce post-hypoglycaemic hyperglycaemia
• Local / systemic allergic reactions
  • itching
  • redness
  • swelling
• lipodystrophy
  • so need rotation of injection sites
• insulin resistance

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