Prilocaine

• As an 0.5 - 2.0% solution for injection
• As a hyperbaric 2% solution for spinal anaesthesia
• As a 3% solution with 0.03units/ml felypressin for dental use

• pKa 7.7
• 33% unionised at physiological pH

• 55% protein bound, therefore relatively short duration of action
• Relative lipid solubility vs. cocaine: 50x (approx. 2x potency)
• Toxic doses:
• Plasma concentration: >5μg/ml
• Dose: 6mg/kg (8mg/kg with felypressin)

• Undergoes hepatic, renal and lung metabolism
• One of its metabolites is o-toluidine
• May precipitate methaemoglobinaemia
• The neonate is especially at risk as its RBC's lack methaemoglobin reductase
• Treatment is with the reducing agents ascorbic acid or methylene blue

• Elimination half-life 100mins