Improved validated assay for the determination of mefloquine and its carboxy metabolite in plasma, serum and whole blood using solid-phase extractionand high-performance liquid chromatography

An improved high-performance liquid chromatography method using a low silan ol activity octadecylsilica column and a solid-phase extraction technique i s validated for the simultaneous analysis of mefloquine and its carboxy met abolite in whole blood, plasma and serum. An octadecylsilica column with hi gh silanol activity is compared to a column of low activity in terms of pH dependent variability of chromatographic retention times for mefloquine and its carboxy metabolite. The low silanol activity column showed a relativel y large mobile phase pH range where retention times for both components are consistent. The solid-phase extraction procedure consists of a simple prot ein precipitation step followed by sample concentration and extraction usin g a C-18 membrane disk. The inter- and intra-assay variability for a therap eutic concentration of mefloquine (1000 ng/ml) is less than 2% in whole blo od, plasma and serum while carboxymefloquine (1000 ng/ml) is 2.3% or less. At concentrations as low as 100 ng/ml the inter-assay variability is 6.2% o r less for both analytes. This method shows a robust analytical procedure f or the simultaneous analysis of mefloquine and its carboxy metabolite where precise measurements are useful in pharmacokinetic studies and in estimati ng drug compliance. (C) 1999 Elsevier Science B.V. All rights reserved.