A More Rapid, Simple and Sensitive HPLC-MS/MS Method for Determination of Epinastine in Human Plasma and Application to a Bioequivalence Study

A rapid, simple and sensitive HPLC-MS/MS method was developed and validated for the determination of epinastine (EPN) using tinidazole as an internal standard (IS). Extraction with acetonitrile (protein precipitation) was used in sample preparation. The prepared samples were chromatographed on a Diamonsil (R) C18 (4.6 x 150 mm, 5 mu m) column by pumping 10 mM ammonium formate with 0.1% formic acid and acetonitrile (55:45, v/v) in an isocratic mode at a flow rate of 0.4 mL/min. Method validation was performed as the FDA guidelines and the standard curves for EPN were found to be linear in the range of 0.100-40.00 ng/mL. The intra-day and inter-day precision and accuracy results were within the acceptable limits. The developed assay method was successfully applied to a bioequivalence study in human volunteers.