Quantification of chlorprothixene, levomepromazine and promethazine in human serum using high-performance liquid chromatography with coulometric electrochemical detection

Abstract

Isocratic reversed-phase high-performance liquid chromatography with coulometric electrochemical detection was optimised to quantify the neuroleptic drugs chlorprothixene, levomepromazine, and promethazine in human serum. The method involves extraction of the neuroleptic drug in n-heptane—isoamylalcohol from the alkalinized serum, followed by chromatographic separation on a Nucleosil CN column with acetonitrile—pyridine—sodium acetate buffer as the mobile phase. The extraction recovery was >85% for each neuroleptic drug. The sensitivity and selectivity required for pharmacokinetic studies was obtained with a dual coulometric analytical cell operating in the oxidative screen mode. The lower limit of detection in human serum for chlorprothixene, levomepromazine, and promethazine, was 0.5, 0.2 and 0.1 ng/ml, respectively. A linear relationship ( r 2 > 0.99) was obtained between the concentrations of each neuroleptic drug and the detector signal. The accuracy of the quality control samples was ± 7% for each neuroleptic drug with a precision within 9.5%, 8.1% and 13.5% for chlorprothixene, levomepromazine, and promethazine, respectively. The neuroleptic drugs were stable in acetonitrile and human serum for at least six months when stored at −20°C. This method is applicable to analyze a large number of serum samples for pharmacokinetic studies of the neuroleptic drugs.