Pharmacokinetics and bioequivalence of eperisone hydrochloride tablet in healthy subjects

Aim To develop a HPLC-ESI-MS assay for determination of eperisone hydrochloride in human plasma and investigate the pharmacokinetics and bioequivalence of two eperisone hydrochloride tablets in human. Methods Buflomedil hydrochloride was used as the internal standard. After alkalized with saturated sodium bicarbonate solution, plasma was extracted with diethylether-cyclohexane (1:1) and separated using HPLC on a reversed-phase C18 column with a mobile phase of 10 mmol x L(-1) ammonium acetate buffer solution (adjusted to pH 3.88 with acetic acid)-methanol (20:80). HPLC-ESI-MS was performed in the selected ion monitoring (SIM) mode using target ions at m/z 260 for eperisone and m/z 308 for the internal standard. A randomized crossover design was performed in 20 healthy volunteers. In the two study periods, a single 100 mg dose of each tablet was administered to each volunteer. Results Calibration curve was linear over the range of 0.02-20 microg x L(-1). The limit of quantification for eperisone hydrochloride in plasma was 0.02 microg x L(-1). The main pharmacokinetics parameters T1/2, Tmax and Cmax were (2.7 +/- 0.4) h, (1.1 +/- 0.5) h and (2.8 +/- 2.8) microg x L(-1) for the reference tablet; (2.8 +/- 0.5) h, (1.1 +/- 0.4) h and (3 +/- 4) microg x L(-1) for the test tablet, respectively. The relative bioavalability of the test tablet was (101 +/- 13)%. Conclusion The assay was proved to be sensitive, accurate and convenient. The two formulations were bioequivalent.