الفهرس 
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Abstract
The present study was designed to evaluate the clinical profile of ropivacaine in different concentrations with that of bupivacaine when given extradullary. Also, the evaluation of the influence of drug concentration on the kinetics of ropivacaine and to compare the kinetics with those bupivacaine.
Results of our showed that ropivacaine is an effective long acting local anesthetic comparable to bupivacaine. The sensory block provided by ropivacaine is similar to that produced by an equal dose and concentration of bupivacaine in extradural blockade, although bupivacaine showed slightly longer duration of sensory analgesia. The motor block produced by ropivacaine 0.5% was less intense and shorter in duration than that after an equal dose of bupivacaine 0.5%. This greater sensory motor separation may prove beneficial in labor analgesia or post-operative pain relief.
Increasing the dose and concentration of ropivacaine from 100mg (20 ml of 0,5% solution) to 200mg (20ml of 1% solution) increases the duration of sensory analgesia and intensifies the motor blockade. Also, significant statistical differences was found between ropivacaine 1% and bupivacaine 0.5% as ropivacaine 1% solution provided a slightly longer duration of sensory analgesia and a more intense motor blockade of longer duration. This can be helpful in surgeries requiring profound motor blockade as in abdominal surgery or orthopedic surgery. As the maximum recommend dose of bupivacaine 0.5% is 150mg, the degree of motor blockade can not be improved by simply increasing the dose of this anesthetic because of the risk systemic toxicity. Ropivacaine was used safely in a dose of 250mg (25ml of 1% solution) by finucane and coworkers in 1996 for abdominal hysterectomy which amounted to 5mg kg -1 in some cases with no evidence of any toxic adverse effect.
Regarding the pharmacokinetic profile of both drugs, results showed greater peak concentrations which occurred after administration of ropivacaine (0.82 + or – 0.03 mg ml -1 for the 1% solution compared to 0.63+ or – 0.02 mg ml -1 for bupivacaine 0.5% solution. Although peak concentrations were higher yet still far below the threshold dose for systemic CNS toxicity which is 3 mg ml -1. This wide safety margin enables us to double the dose of ropivacaine without fear of toxicity.