EXTRADURAL S(-)-BUPIVACAINE - COMPARISON WITH RACEMIC RS-BUPIVACAINE

Bupivacaine has a chiral centre and is currently available as a racemi c mixture of its two enantiomers: R(+)-bupivacaine and S(-)-bupivacain e. Preclinical studies have demonstrated that there is enantiomer sele ctivity of action with the bulk of central nervous system and cardiova scular toxicity residing with the R(+) isomer. The aim of this study w as to compare the clinical efficacy and safety of S(-)-bupivacaine wit h racemic RS-bupivacaine for extradural anaesthesia. We studied 88 pat ients undergoing elective tower limb surgery under lumbar extradural a naesthesia who received 15 mi of 0.5% or 0.75% S(-)-bupivacaine, or 0. 5% RS-bupivacaine in a randomized, double-blind study. There was no di fference in onset time, maximum spread of sensory block or intensity o f motor block between the three groups. Duration of sensory block was significantly longer for 0.75% S(-)-bupivacaine. We conclude that S(-) -bupivacaine has similar local anaesthetic characteristics to RS-bupiv acaine when used for extradural anaesthesia.