Pharm 101: Insulin

Class

Endogenous hormone

Mechanism of action

• Acts on ligand-regulated tyrosine kinase receptor
• Promotes uptake of glucose from blood into tissues, especially fat, liver, skeletal muscle
• Promotes glycogen synthesis

Formulations

• IV or SC administration
• Rapid and short acting:
  • Clear solution, neutral pH
  • Rapid onset, short duration
  • e.g. insulin lispro
  • Short-acting regular soluble insulin is used for IV infusion, as it immediately dissociates on dilution and thus is able to be more precisely delivered
• Intermediate acting:
  • Turbid solution, neutral pH
  • Protamine in phosphate buffer (NPH) to prolong action
  • e.g. insulin aspart protamine
• Long-acting:
  • Clear solution
  • Slow onset, prolonged action
  • Daily administration mimics basal insulin secretion
  • e.g. insulin glargine

Clinical uses

• Regulation of blood glucose:
  • Combinations of insulins with different durations of actions (see below) aim to replace basal insulin requirement (50%) and meal requirement (50%) to achieve optimal glycaemic control
• Hyperkalaemia
• Calcium channel blocker overdose

Adverse effects

• Hypoglycaemia
• Hypoglycaemia unawareness
• Allergy (usually due to non-insulin contaminants)
• Immune insulin resistance
• Lipodystrophy at injection sites

References

• Katzung BG. Basic and Clinical Pharmacology. 14e. 2018