Abstract: AimTo establish an HPLC-fluorescent spectrometric method for the determination of mexiletine hydrochloride in plasma after derivatization with fluram. MethodsFluram acetone solution was added to the deproteinized plasma with acetone to obtain the derivative of mexiletine. The HPLC method was performed on a column of Allitima C₁₈ (150 mm×4.6 mm, 5 μm) with the mobile phase of methanol-water-diethylamine-phosphoric acid buffer (2.4 mol·L^-1, pH 4.0) (70∶28∶2), and the detective wavelength were set at E_x 392 nm and E_m 480 nm. ResultsMexiletine has a liner range over the concentration range from 0.100-6.400 mg·L^-1. The lowest detectable concentration of this method was 5 μg·L^-1 (S/N≥4). The intra-day and inter-day RSDs were 1.34%-5.31%, respectively. ConclusionThis method is simple, selective and can be used for therapeutic drug monitoring (TDM) and pharmacokinetic studies of mexiletine.