Bioequivalence and Analytical Validation of Tizanidine in Human Plasma Using LC -MS/MS

This study presents a detailed bioequivalence analysis and method validation for quantifying tizanidine hydrochloride (TIZ) in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The analytical method incorporates internal standardization with amlodipine besylate, achieving high sensitivity and specificity through multiple reaction monitoring (MRM). A robust linear calibration curve (۵۵–۳۲۵۵ ppt) was established, weighted by ۱/x, with a correlation coefficient exceeding ۵۹۲۲. Analytical method validation adhered to ICH M ۱۵ guidelines, ensuring accuracy, precision, specificity, and robustness. The liquid-liquid extraction protocol optimized sample preparation, while system suitability was confirmed through key performance parameters, including retention time stability and signal-to-noise ratios. Bioequivalence was evaluated in a single-dose crossover study with healthy volunteers, comparing test and reference formulations. Pharmacokinetic parameters such as maximum plasma concentration (Cmax), time to reach Cmax (Tmax), and area under the curve (AUC) were statistically analyzed, meeting regulatory acceptance criteria. The methodology demonstrated negligible matrix effects and interference, enabling precise quantification of TIZ at therapeutic concentrations. These findings confirm the reliability of this validated LC-MS/MS method for bioequivalence studies and therapeutic drug monitoring of tizanidine.

Keywords:

Tizanidine hydrochloride , LC-MS/MS , Bioequivalence , Analytical method validation , Pharmacokinetics , Liquid-liquid extraction