LC/ESI-MS method for the determination of trimetazidine in human plasma: application to a bioequivalence study on Chinese volunteers

A rapid liquid chromatography electrospray ionization mass spectrometry (LC/ESI-MS) method with good sensitivity and specificity has been developed and validated for the identification and quantification of trimetazidine in human plasma. Trimetazidine and lidocaine (internal standard) were isolated from plasma samples by protein precipitation with methanol. The chromatographic separation was accomplished on a Xterra MS C₁₈ Column (150 mm × 4.6 mm, 5 μm particle size) with the mobile phase consisting of methanol and water (40:60, v/v) (pH 2.0, adjusted with trifluoroacetic acid), and the flow rate was set at 0.6 mL/min. Detection was performed on a single quadruple mass spectrometer by selected ion monitoring (SIM) mode (m/z 267.0 for trimetazidine and m/z 235.0 for lidocaine) with the retention time at about 3.47 and 5.05 min, respectively. The calibration curve for trimetazidine was satisfactory with regression coefficient 0.9995 over the range of 2.5–100 ng/mL in the plasma. The LOQ (S/N = 10) was accordingly 2.5 ng/mL. The intra-day and inter-day precision expressed as relative standard deviation was 2.83–6.10% and 4.83–5.82%. The method was successfully applied to investigate the bioequivalence between two kinds of tablets (test versus reference product) in 19 healthy male Chinese volunteers. After a single 20 mg dose for the test and reference product, the resulting mean of major pharmacokinetic parameters such as AUC_0–24, AUC_0−∞, C_max, T_max and t_1/2 of trimetazidine were (673.1 ± 117.6 ng h mL⁻¹ versus 652.3 ± 121.9 ng h mL⁻¹), (717.1 ± 120.9 ng h mL⁻¹ versus 692 ± 128.6 ng h mL⁻¹), (74.85 ± 12.13 ng mL⁻¹ versus 71.93 ± 14.32 ng mL⁻¹), (2.312 ± 0.663 h versus 2.211 ± 0.608 h) and (4.785 ± 0.919 h versus 4.740 ± 0.823 h), respectively, indicating that these two kinds of tablets were bioequivalent in the Chinese population.