[Determination of tamsulosin in dog plasma by a high sensitive liquid chromatography-tandem mass spectrometric...

To develop and validate a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the determination of tamsulosin in dog plasma after oral administration of controlled-release tablet of tamsulosin hydrochloride, the samples and the internal standard, diphenhydramine, were extracted from dog plasma by n-hexane-dichloromethane (2 : 1), and separated on a Bonchrom XBP-C18 column using a mobile phase consisted of methanol-acetonitrile-ammonium formate (10 mmol x L(-1)) (30 : 40 : 30, v/v/v), at a flow rate of 0.4 mL x min(-1). Mass spectrometric detection was operated on a triple quadrupole tandem mass spectrometer equipped with atmospheric pressure chemical ionization (APCI) source in positive mode. Quantification was performed using selected reaction monitoring (SRM) of the transitions m/z 409 --> 228 for tamsulosin and m/z 256 --> 167 for the internal standard, respectively. The linear concentration ranges of the calibration curves for tamsulosin were 0.02 - 50 ng x mL(-1). The lower limit of quantification was 0.02 ng x mL(-1). The accuracy ranged from -2.61% to 8.82% in terms of relative error (RE). The intra- and inter-day relative standard deviation (RSD) across three-run validations were lower than 9.72%. The method was proved to be highly sensitive, selective, and had been successfully applied to the pharmacokinetic study after an oral administration of 0.4 mg tamsulosin hydrochloride controlled release preparations to dogs.