Bupivacaine

• Presents as a racemic mixture of the S- and R-enantiomers
• Comes as solutions of 0.125%, 0.25% and 0.5% solutions ± 1:200,000 adrenaline
• NB adrenaline does not alter safe dose of bupivacaine, which remains 2mg/kg
• Can be mixed with 80mg/ml glucose to form heavy bupivacaine (specific gravity 1.026) for use in spinals

• An enantiopure preparation of S-bupivacaine
• Reduced toxicity when information from animal studies and human volunteers is extrapolated, because:
• The dose required to produce myocardial depression is higher
• The excitatory CNS effects occur at a higher dose than bupivacaine

• pKa 8.1
• Means only 15% unionised at physiological pH, giving it a slow onset time

• 95% protein bound
• Relative lipid solubility vs. cocaine: 1000x (therefore 8x potency)
• Toxic doses:
• Plasma concentration: >1.5μg/ml
• Dose: 2mg/kg (unchanged by adrenaline)

• Hepatic dealkylation to pipecolic acid and pipecolylxylidine

• Elimination half-life 160mins