INSULIN

Hormone that plays a key role in regulation of carbohydrate, fat and protein metabolism. Soluble insulin, short-acting form, is suitable for diabetic emergencies and during surgery. Isophane insulin is intermediate-acting insulin. Biphasic isophane insulin is premixed with both properties of short- and immediate-acting insulin. Insulin zinc suspension is a long-acting insulin

Dosage Forms

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Injection

Soluble insulin 100 IU/ml
Biphasic isophane insulin; Soluble insulin 30% + isophane insulin 70% 100 IU/ml
Insulin isophane 100 IU/ml
Insulin zinc suspension 100 IU/ml

Uses

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  • Diabetes mellitus
  • Diabetic ketoacidosis

Dose and Duration

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Appropriate insulin regimens should be worked out for each patient basing on the individual blood sugar levels

Diabetes mellitus
Adult: Isophane insulin, 10-20 IU twice daily SC injection

Soluble insulin, 40–100 IU SC daily in 3 divided doses before meals

Child: Isophane insulin 5-10 IU twice daily SC injection

Soluble insulin, 40–80 IU SC daily in 3 divided doses before meals

Note: Conventional insulin therapy often combines the two types of insulin in a mixture of 30/70 soluble to isophane insulin. Usually given twice daily or once daily in elderly. A common preparation is Mixtard®. Long-acting insulin is usually given once daily.
Diabetic ketoacidosis
Start an IV infusion of soluble insulin, diluted and mixed thoroughly with sodium chloride 0.9% to a concentration of 1 unit/ml; infuse at a rate of 0.1 units/kg/hour
Monitor urine and blood glucose and ketones hourly and adjust insulin infusion accordingly. Once blood glucose concentration falls below 14 mmol/litre, give glucose 10% (into a large vein) at a rate of 125ml/hour in addition to sodium chloride 0.9% infusion. Continue infusion until blood ketone concentration is below 0.3mmol/litre. If patient is able to drink and eat, ideally give SC soluble insulin and a meal, then stop infusion 1 hour later.

Contraindications

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  • Depression in children
  • Severe liver disease

Side Effects

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  • Hypoglycaemia
  • Local reactions and hypertrophy at injection site
  • Allergic reactions

Interactions

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  • Beta blockers e.g. atenolol, propranolol (mask hypoglycaemic symptoms so patient cannot recognise them)
  • Corticosteroids (cause insulin resistance and hyperglycaemia)
  • Bendroflumethiazide (hypoglycaemic effect antagonised)
  • Furosemide (hypoglycaemic effect antagonised)
  • Oestrogens (hypoglycaemic effect antagonised)

Patient Instructions

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  • Always inject insulin at least 15–30 minutes before food
  • Never take the medicine when you have skipped a meal
  • Avoid overdose as this will cause dangerously low blood sugar
  • Alternate injection site to avoid scarring in one site
  • Symptoms of dangerously low blood sugar include: shaking (tremors), tiredness, unconsciousness. Take 2 teaspoons of glucose or sugar or sugary soft drink as first aid, as well as long-acting carbohydrate (e.g. bread) to restore liver glycogen. Report to the nearest health centre immediately
  • Consider self-monitoring of blood glucose to help you be in better control of your blood glucose levels

Pregnancy

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  • Can be used

Breast-feeding

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  • Can be used

Storage

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  • Store at 2–8°C (cold storage). Do not freeze

⚠️ Caution

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  • Insulin is given by subcutaneous injection into the upper arms, thighs, buttocks, or abdomen. Teach patient how to measure dose and inject insulin properly
  • There may be increased absorption from a limb site, if limb is used in strenuous exercise following the injection
  • Use only syringes calibrated for the particular concentration of insulin administered
  • Injection site should be rotated to prevent lipodystrophy
  • Instruct patient how to avoid hypoglycaemia
  • During pregnancy and breast-feeding, insulin requirements alter and doses should be assessed frequently by a physician
  • Insulin requirements may be affected by variations in lifestyle (diet and exercise), concomitant use of drugs such as corticosteroids, presence of infections, stress, accidental or surgical trauma, puberty and pregnancy (2nd and 3rd trimesters) which tend to increase insulin needs
  • Renal or hepatic impairment and some endocrine disorders (e.g. Addison disease and hypopituitarism) or coeliac disease, usually reduce requirements