ROPIVACAINE - A REVIEW OF ITS PHARMACOLOGY AND THERAPEUTIC USE IN REGIONAL ANESTHESIA

The enantiomerically pure (S-enantiomer) amide local anaesthetic drug ropivacaine blocked nerve fibres responsible for transmission of pain (A delta and C fibres) more completely than those that control motor f unction (A beta fibres) in in vitro studies. The drug shares the bipha sic vascular effects common to the amide local anaesthetic drug class. In vitro studies indicate that ropivacaine is less cardiotoxic than e quimolar concentrations of bupivacaine. Apart from one trial in women undergoing hysterectomy, clinical studies that compared the efficacy o f different doses of epidurally administered ropivacaine in patients u nder going various surgical procedures did not reveal any consistent d ose-related differences with respect to sensory blockade. However moto r blockade did become more intense as the dose of ropivacaine increase d Overall, direct comparisons show that epidural ropivacaine is less p otent than epidural bupivacaine when the 2 drugs are administered at t he same concentration. However, this difference is less marked in term s of sensory blockade than motor blockade. The greater degree of separ ation between motor and sensory blockade seen with ropivacaine relativ e to bupivacaine is more apparent at the lower end of the dosage scale . Nevertheless, higher doses of ropivacaine than bupivacaine are gener ally required to elicit equivalent anaesthetic effects. Ropivacaine ha s been shown to induce successful brachial plexus anaesthesia when giv en at a concentration of 5 mg/ml, but not 2.5 mg/ml, and was as effect ive as bupivacaine in comparative studies in this indication. Limited data indicate that continuous epidural infusion of ropivacaine postope ratively reduces postsurgical pain in a dose-related manner Morphine c onsumption was also reduced. Higher doses of ropivacaine were signific antly more effective than placebo. Similarly ropivacaine controlled po stsurgical pain when infiltrated directly into surgical wound sites (i .e. wound infiltration) and was as effective as bupivacaine, and more effective than placebo, in this regard. Adverse events associated with epidurally administered ropivacaine include hypotension, nausea, brad ycardia, transient paraesthesia, back pain, urinary retention and feve r. The drug appears to have an adverse event profile similar to that o f bupivacaine. In animal studies, overdoses of ropivacaine were better tolerated than overdoses of bupivacaine but not lidocaine (lignocaine ). Human volunteers tolerated a higher intravenous dosage of ropivacai ne than bupivacaine before developing initial signs of toxicity Thus, ropivacaine, according to animal data, is less cardiotoxic than bupiva caine. Based on available clinical data, ropivacaine appears to be as effective and at ell tolerated as bupivacaine when equianalgesic doses are compared The greater degree of separation between motor and senso ry blockade seen with ropivacaine relative to bupivacaine at lower con centrations (similar to 5 mg/ml) will be advantageous in certain appli cations.