Simultaneous determination of lidocaine and bupivacaine in human plasma: application to pharmacokinetics.

High-performance liquid chromatography has been applied to the simultaneous determination of lidocaine and bupivacaine levels in human plasma, using etidocaine as internal standard. The method was found to be linear in the range 10-2,000 micrograms/l for lidocaine and 20-1,000 micrograms/l for bupivacaine. Within-day and day-to-day coefficients of variation were generally lower than 12%. The method was applied to a pharmacokinetic study of lidocaine and bupivacaine during peribulbar anesthesia in ocular surgery. Both compounds displayed a slow apparent elimination rate. The method described here permitted the determination of the complete pharmacokinetic profiles of the two anesthetics, although they were administered at quite different doses.