RAPID SIMULTANEOUS DETERMINATION OF LIDOCAINE, BUPIVACAINE, AND THEIR2 MAIN METABOLITES USING CAPILLARY GAS-LIQUID-CHROMATOGRAPHY WITH NITROGEN PHOSPHORUS DETECTOR

A gas-liquid chromatographic method for the simultaneous measurement i n serum of bupivacaine, lidocaine, and their main metabolites, 2,6-pip ecolylxylidide (PPX) and monoethylglycine xylidide (MEGX), respectivel y, is described. The procedure involves a one-step extraction and inje ction of the extract into a gas chromatograph equipped with a capillar y column and nitrogen phosphorus detector under constant temperature c onditions. Recovery of all components averaged 94%, with the lowest de tection limit of 15 ng/ml for the four drugs. The precision within-ser ies coefficients of variation ranged from 7.7% for bupivacaine, 8.6% f or lidocaine, 10.2% for MEGX, and 15.8% for PPX. The interday coeffici ents ranged from 0.7 to 6.5%. Concomitant use of caffeine and carbamaz epine may interfere with MEGX and bupivacaine determination, respectiv ely. For this reason, in patients receiving one of these two drugs (or ingesting foods and beverages containing caffeine), the described met hod is not recommended.