Abstract: AIM: To establish an LC-MS/MS method for the determination of tamsulosin in dog plasma and to study pharmacokinetics of tamsulosin hydrochloride controlled release capsules in Beagle dogs.METHODS: The 0.3 mL of blood samples were collected at before and different times after six Beagle dogs were received an oral dose of 0.4 mg tamsulosin.Tamsulosin and the internal standard (guaifenesin) were extracted by ethyl acetate from dog plasma, and separated on a Thermo C₁₈ column using methanol-water-formic acid (80∶20∶0.2, V/V/V) as mobile phase. Elecrospray ionization (ESI) source was applied and operated in the positive ion mode. Quantification was performed using selected reaction monitoring (SRM) mode. The transitions for tamsulosin and guaifenesin were m/z 409.0→m/z 228.0 and m/z 199.0→m/z 125.0, respectively.RESULTS: The linear concentration ranges of the calibration curves for tamsulosin were 0.05-10.0 ng/mL.The lower limit of quantification was 0.05 ng/mL. The intra- and inter-run relative standard deviations (RSD) were lower than 13.4%.The pharmacokinetic parameters of tamsulosin was as follows: AUC_{0-24 h}(7.82±1.92) ng·h·mL^-1, AUC_0-∞ (8.04±2.02) ng·h·mL^-1,t_1/2 (2.96±2.13) h.CONCLUSION: The method is simple,high sensitivity and is proved to be suitable for pharmacokinetic study for tamsulosin in Beagle dogs.The half-life is short, and its clearance from dog body is very quick.

Key words: LC-MS/MS, Tamsulosin, Pharmacokinetics