Primary evaluation of the local anaesthetic properties of the amino amide agent ropivacaine (LEA 103)

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Abstract
The local anaesthetic properties of l‐propyl‐2′,6′‐pipecoloxylidide, a congener of mepivacaine and bupivacaine, and its enantiomers were compared in animals. The (S)‐enantiomer (ropivacaine, LEA 103) produced a longer duration of sciatic nerve block and infiltration anaesthesia than the racemate and the (R)‐form. Ropivacaine and bupivacaine were equally potent in terms of block of evoked action potentialin vitroand minimum effective concentrationin vivo.Ropivacaine 0.25–1.0% was distinctly longer acting than bupivacaine on infiltration, equally effective in sciatic and brachial plexus block and somewhat shorter lasting in epidural and spinal blockade. There were tendencies towards a greater benefit from the addition of adrenaline with ropivacaine in epidural anaesthesia and a shorter latency to block in some of the tests. Ropivacaine seems less vasodilative than bupivacaine and capable of producing some vasoconstriction over a wider range of low concentrations, which may explain its longer duration of intradermal anaesthesia. The somewhat shorter duration of central blockade of ropivacaine is probably a result of lesser lipid solubility. Ropivacaine was less toxic (i.v. and s.c. LD50‐values) than bupivacaine but more toxic than lidocaine, and produced only weak local irritation. Due to a combination of interesting local anaesthetic properties and relative safety including cardiotoxic potential, we consider ropivacaine a candidate for further studies.