Ropivacaine - An update of its use in regional anaesthesia

Ropivacaine is a long-acting, enantiomerically pure (S-enantiomer) amide lo cal anaesthetic with a high pK(a) and low lipid solubility which blocks ner ve fibres involved in pain transmission (A delta and C fibres) to a greater degree than those controlling motor function (A beta fibres). The drug was less cardiotoxic than equal concentrations of racemic bupivacaine but more so than lidocaine (lignocaine) in vitro and had a significantly higher thr eshold for CNS toxicity than racemic bupivacaine in healthy volunteers (mea n maximum tolerated unbound arterial plasma concentrations were 0.56 and 0. 3 mg/L, respectively). Extensive clinical data have shown that epidural ropivacaine 0.2% is effect ive for the initiation and maintenance of labour analgesia, and provides pa in relief after abdominal or orthopaedic surgery especially when given in c onjunction with opioids (coadministration with opioids may also allow for l ower concentrations of ropivacaine to be used). The drug had efficacy gener ally similar to that of the same dose of bupivacaine with regard to pain re lief but caused less motor blockade at low concentrations. Lumbar epidural administration of 20 to 30ml ropivacaine 0.5% provided anae sthesia of a similar quality to that achieved with bupivacaine 0.5% in wome n undergoing caesarean section, but the duration of motor blockade was shor ter with ropivacaine. For lumbar epidural anaesthesia for lower limb or gen itourinary surgery, comparative data suggest that higher concentrations of ropivacaine (0.75 or 1.0%) may be needed to provide the same sensory and mo tor blockade as bupivacaine 0.5 and 0.75%. In patients about to undergo upp er limb surgery, 30 to 40ml ropivacaine 0.5% produced brachial plexus anaes thesia broadly similar to that achieved with equivalent volumes of bupivaca ine 0.5%, although the time to onset of sensory block tended to be faster a nd the duration of motor block shorter with ropivacaine. Ropivacaine had an adverse event profile similar to that of bupivacaine in clinical trials. Several cases of CNS toxicity have been reported after ina dvertent intravascular administration of ropivacaine, but only 1 case of ca rdiovascular toxicity has been reported to date. The outcome of these inadv ertent intravascular administrations was favourable. Conclusion: Ropivacaine is a well tolerated regional anaesthetic with an ef ficacy broadly similar to that of bupivacaine. However, it may be a preferr ed option because of its reduced CNS and cardiotoxic potential and its lowe r propensity for motor block.