High-Performance Liquid Chromatographic Assay for Meptazinol and Metabolite in Plasma and Urine Using a Silica Gel Column and an Aqueous Mobile Phase

Abstract

An HPLC method for quantitating meptazinol, a synthetic narcotic analgesic, and its glucuronide in plasma and urine is presented. the method involves extraction from plasma with methylene chloride under alkaline conditions (pH = 9.7). Urine samples are injected without further preparation following addition of internal standard. the conjugate metabolite of meptazinol was hydrolyzed with β-glucuronidase. Samples are analyzed using an Ultrasphere Si column with an aqueous mobile phase of 65% acetonitrile and 5 mM dibasic ammonium phosphate at pH = 7.0. the flow rate is 1.0 ml/min. Fluorescent detector settings were 275 nm and 315 nm for excitation and emission wavelengths, respectively. Detection limits were 2 and 5 ng/ml in plasma and 50 and 70 ng/ml in urine for meptazinol and the hydrolyzed glucuronide, respectively. the coefficients of variation for interday and intraday precision were less than 10%. This method has been used in pharmacokinetic studies of i.v. and i.m. formulations involving 1360 plasma and 640 urine samples.