Simultaneous determination of meperidine and normeperidine in biofluids

A method employing solvent extraction and gas-liquid chromatography has been developed for the simultaneous determination of meperidine and its N-demethylated metabolite, normeperidine, in biofluids. Normeperidine is analyzed as the heptafluorobutyryl derivative. Using a flame ionization detector, the lower limit of sensitivity of the method is 0.02 mug/ml of biofluid for both compounds. Samples of plasma obtained from obstetrical patients, following a single therapeutic dose, were found to contain higher levels of meperidine than concurrent samples of amniotic fluid. Normeperidine could not be detected in either biofluid after a single dose. There is, however, a gradual accumulation of normeperidine in plasma after repeated doses as determined in samples from cancer patients. The method can also be used to determine the disposition of merperidine and the accumulation of normeperidine in the cat.