Determination of tamsulosin in plasma of healthy Chinese male subjects by a novel and simple LC-MS/MS method and its application to pharmacokinetic studies

Tamsulosin, the first highly selective alpha 1-adrenoceptor antagonist, is widely used for urination disorders caused by benign prostatic hyperplasia (BPH). The pharmacokinetics and safety of 0.2 mg tamsulosin hydrochloride sustained-release capsules were evaluated in 60 healthy Chinese male subjects under fasting and fed conditions in this study. A simple, sensitive, and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of tamsulosin in human plasma, which has been applied to pharmacokinetic study. The analyte and internal standard (tamsulosin-d5) were extracted by protein precipitation, and separated on a ZORBAX Eclipse XDB-C18 column (4.6 x 50 mm,1.8 mu m; Agilent Tech) using a gradient elution with mobile phases methanol and 5 mM ammonium acetate. The linear range was 0.05-15.0 ng/ mL. It showed good selectivity in normal, hyperlipidemic, and hemolyzed blank matrices. The CV (%) of intra-batch precision was <4.4% and the RE (%) of accuracy was in the range of -5.0%-6.7%; the CV (%) of inter-batch precision was <-5.8% and the RE (%) of accuracy was in the range of 1.2%-4.0%. The mean extraction recovery for the analyte was 102.1 +/- 3.75% and for the IS was 102.2 +/- 2.00%. Two formulations were considered bioequivalent under fasting and fed conditions, and the 90% confidence intervals for the geometric mean test/reference ratios were within the predetermined range of 80%-125%. A single oral dose of 0.2 mg tamsulosin hydrochloride sustained-release capsule was well-tolerated throughout the clinical trial, and no > Grade 1 adverse events (AEs) and serious AEs occurred during the trial.