FRCA Notes


Amethocaine


  • Amethocaine is an ester-linked local anaesthetic used primarily for topical anaesthesia
  • 0.5% or 1% drops for topical use (may initially produce a burning sensation)
  • 4% cream for topical anaesthesia to the skin
    • Onset 30mins
    • Causes local histamine release and vasodilation
    • Effects last 4-6hrs

Absorption

  • pKa 8.5
  • 7% unionised at physiological pH, giving it a slow onset time

Distribution

  • 75% protein bound
  • Relative lipid solubility vs. cocaine: 200x

Metabolism

  • Ester hydrolysis

Excretion

  • Elimination half-life 80mins