DETERMINATION OF BACLOFEN IN HUMAN PLASMA AND URINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

An isocratic reversed-phase column liquid chromatographic assay for ba clofen was developed. Prior to analysis, derivatization of urine or de proteinized plasma with 4-chloro-7-nitrobenzofurazan (NBD-CI) reagent was employed. After solid-phase extraction on a small silica gel colum n, the mixture was chromatographed on a 10 mu m Bondapak C-18 column u sing methanol-water (45 + 55 v/v) as the mobile phase, The NBD-baclofe n derivative was detected spectrofluorimetrically by monitoring the em ission at 524 nm with excitation at 463 nm. The method was tested for suitability in routine analysis. After a single oral dose of 20 mg of baclofen, the plasma concentration and the cumulative urinary excretio n of the drug were determined. The average recoveries were 99.5 and 98 .5% for plasma and urine, respectively.