Levobupivacaine

Levobupivacaine ((S)-1-butyl-N-(2,6-dimethylphenyl)piperidine-2-carboxamide; CAS 27262-47-1; molecular formula C18H28N2O; molecular weight 288.43) is the (S)-enantiomer of bupivacaine, developed by Chiroscience and Purdue and approved by the FDA in 1999 (Chirocaine). The enantioselective pharmacology of bupivacaine motivated separation: the (R)-enantiomer carries the dominant cardiotoxic and CNS toxic burden through higher cardiac sodium channel affinity and slower dissociation, while the (S)-enantiomer produces equivalent neural block with substantially reduced toxic margin. Direct toxicology comparisons in rat and pig models show 30 to 40 percent lower toxic dose ratios for cardiovascular collapse and seizure threshold with levobupivacaine versus racemic bupivacaine at equivalent neural block efficacy. Clinical equivalence trials in epidural, spinal, and peripheral nerve block applications demonstrate non-inferior efficacy with lower incidence of CNS toxicity in inadvertent intravascular dosing. Mechanism is identical to racemic bupivacaine (voltage-gated sodium channel block) with the favorable enantioselectivity at cardiac sodium channels driving the safety advantage. Onset, duration, and toxic margins are characterized relative to bupivacaine, with the reduced cardiotoxicity reflecting the (S)-enantiomer pharmacology. The principal limitation of levobupivacaine is acquisition cost relative to racemic bupivacaine, which has restricted uptake in some markets despite the favorable safety profile. The compound was withdrawn from the US market in 2010 for commercial reasons but remains available in Europe and Asia. Lipid emulsion rescue is the standard therapy for any LAST event.