Liquid chromatographic-tandem mass spectrometric method for the simultaneous quantitation of telmisartan and hydrochlorothiazide in human plasma.

A rapid and sensitive method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the simultaneous determination of telmisartan and hydrochlorothiazide in human plasma. Sample preparation involved liquid-liquid extraction with diethyl ether-dichloromethane (60:40, v/v). The analytes and internal standard, probenecid, were separated on a Venusil XBP-C(8) column using gradient elution with acetonitrile-10 mM ammonium acetate-formic acid at a flow rate of 1.2 mL/min. Detection was by electrospray negative ionization mass spectrometry using multiple reaction monitoring of the transitions at m/z 513.0-->469.4 for telmisartan, m/z 295.9-->268.9 for hydrochlorothiazide and m/z 283.9-->239.9 for probenecid. For both analytes, the method was linear in the range 1.00-600 ng/mL with intra- and inter-day precision (as relative standard deviation) <or=10.6% and accuracy (as relative error) <or=4.2%. The assay was successfully applied to a pharmacokinetic study in 9 healthy volunteers given a single oral dose of a combination tablet containing telmisartan 80 mg and hydrochlorothiazide 12.5 mg.