Determination of silodosin in human plasma by liquid chromatography–tandem mass spectrometry

A rapid, sensitive and specific liquid chromatography–tandem mass spectrometric (LC–MS/MS) method has been developed and validated for the determination of silodosin in human plasma. Silodosin and internal standard (IS) were extracted from human plasma by liquid–liquid extraction using methyl t-butyl ether and analyzed on an Agilent C8 column with the mobile phase of acetonitrile–10 mM ammonium acetate (40:60, v/v) adjusted to pH 4.5 with acetic acid. Detection was carried out by MS/MS using TurboIonSpray (TIS) ionization and multiple reaction monitoring (MRM) in the positive-ion mode. The mass transitions monitored were m/z 496.3 → 261.4 and m/z 440.4 → 259.3 for silodosin and IS, respectively. The standard curve was linear in the range of 0.50–50.0 ng/ml with intra- and inter-day precision of 3.2–7.2% and 2.0–7.5%, respectively. The lower limit of quantification (LLOQ) for silodosin was 0.50 ng/ml using 500 μl plasma sample. This method was successfully applied to the pharmacokinetic study in healthy volunteers.