PHARMACOKINETICS AND CLINICAL EFFECT DURING CONTINUOUS EPIDURAL INFUSION WITH ROPIVACAINE 2.5 MG ML OR BUPIVACAINE 2.5 MG/ML FOR LABOR PAINRELIEF/

Background: Ropivacaine has shown less systemic toxicity than bupivaca ine, and comparatively low muscle-blocking properties could constitute another advantage when used epidurally for obstetric pain relief. We aimed primarily to compare maternal and foetal drug disposition follow ing continuous epidural infusion of ropivacaine or bupivacaine. Method s: Twenty-four full-term, nulliparous women were randomized to continu ous epidural infusion (10 ml/h) of ropivacaine 2.5 mg/ml or bupivacain e 2.5 mg/ml for labour pain relief in a double-blind, parallel-group d esign. Maternal blood samples were collected up to 24 h after the end of infusion as well as taken from the umbilical cord at the time of de livery. Sensory and motor block as well as analgesia were assessed. Al l the women were monitored by cardiotocography and neonatal assessment was performed. Results: The sensory block was adequate for both drugs . Higher plasma levels (total and free) were seen with ropivacaine, al though the infusion with bupivacaine continued on average for about 2 hours longer. However, the ratios between maternal and umbilical blood concentrations were similar for both drugs. Normal neonatal Apgar and neonatal adaptive capacity scores (NACS) were found in both groups. C onclusion: A continuous epidural infusion of 25 mg/h ropivacaine or bu pivacaine both produced good labour pain relief. Higher total and free plasma concentrations were seen for ropivacaine. The ratios between m aternal and umbilical plasma levels were similar for both drugs.