Mitochondrial effects of L-ropivacaine, a new local anesthetic

The effects of the local anesthetics ropivacaine and bupivacaine were inves tigated on isolated rat liver mitochondria. The efficiency of oxidative pho sphorylation was evaluated by measuring the rates of respiration and ATP sy nthesis and the magnitude of the transmembrane electrical potential (Delta psi). Bupivacaine did not alter the ADP-stimulated respiration but strongly affected the resting respiration, which was more than doubled at 0.6 mM. I n addition, it decreased the transmembrane electrical potential, and the AT P synthesis rate (Delta psi was less than 100 mV at 0.6 mM). Ropivacaine di d not alter the ADP stimulated respiration, and the resting respiration see med to be substantially unaffected up to 1.2 mM; a slight increase was obse rved at 1.8 and 2.4 mM. The transmembrane potential was decreased by anesth etic concentrations higher than 1.2 mM and ATP synthesis was consequently a ffected. The findings suggest that ropivacaine is less toxic than bupivacai ne, in rat liver mitochondria. BIOCHEM PHARMACOL 56;12:1633-1637, 1998. (C) 1998 Elsevier Science Inc.