High-performance liquid chromatography-electrospray ionization-mass spectrometric determination of emedastine difumarate in human plasma and its pharmacokinetics.

A selective and sensitive method employing high-performance liquid chromatography (HPLC)-electrospray ionization (ESI)-mass spectrometry is developed and validated for the determination of emedastine difumarate in human plasma. With naphazoline hydrochloride as the internal standard, emedastine difumarate is extracted from plasma with ethyl acetate. The organic layer is evaporated, and the residue is redissolved in the mobile phase. An aliquot of 10 microL is chromatographically analyzed on a prepacked Phenomenex Luna 5u CN 100A (150 x 2.0-mm i.d.) column, using a mobile phase comprised of methanol-water (20 mM CH(3)COONH(4), pH 4.0) (80:20, v/v). Standard curves are linear (r(2) = 0.9990) over the concentration range of 0.05-30 ng/mL and had good accuracy and precision. The within- and between-batch precisions did not exceed 15% for the relative standard deviation. The lower limit of detection is 0.01 ng/mL. The validated HPLC-ESI-MS method is successfully used to study emedastine difumarate pharmacokinetics in 12 healthy volunteers.