Determination of lomerizine in human plasma by liquid chromatography/tandem mass spectrometry and its application to a pharmacokinetic study

• We first applied HPLC–MS/MS method to determine lomerizine in human plasma.
• Our HPLC–MS/MS method for the quantification of lomerizine was fully validated.
• We improved the LLOQ of lomerizine in human plasma from 5 ng/mL to 0.1 ng/mL.
• We performed an application on 18 healthy volunteers for a pharmacokinetic study.

A rapid, sensitive and selective high performance liquid chromatography–electrospray ionization–tandem mass spectrometry method (HPLC–ESI–MS/MS) was developed and validated for the determination and pharmacokinetic investigation of lomerizine in human plasma. Protein precipitation process was used to extract lomerizine from human plasma. Plasma samples were separated by HPLC on an Agela Venusil XBP Phenyl column (100 mm × 2.1 mm, 5 μm) using a mobile phase consisting of methanol-2 mM ammonium acetate-formic acid (70:30:0.1, v/v/v) and the flow rate was set at 0.35 mL/min. The total run time was 4.0 min and the elution of lomerizine was at 1.9 min. The detection was performed on a triple quadrupole tandem mass spectrometer in the multiple reaction-monitoring (MRM) mode using the respective [M + H]+ ions m/z 469.2 → 181.0 for lomerizine and m/z 405.2 → 202.9 for the I.S. The calibration curve was linear over the range of 0.1–25 ng/mL (r2 > 0.99) with a limit of quantitation (LOQ) of 0.1 ng/mL. The intra- and inter-day precision (relative standard deviation, RSD) values were below 9.65% and the mean accuracy was from 99.00 to 103.00% at four quality control levels. Lomerizine was stable during stability studies, i.e., long term, auto-sampler and freeze/thaw cycles. The method was successfully applied for the evaluation of pharmacokinetics of lomerizine after single oral doses of 10 mg lomerizine to 18 healthy volunteers.