LC-MS/MS method for simultaneous estimation of candesartan and hydrochlorothiazide in human plasma and its use in clinical pharmacokinetics.

BACKGROUND: ATACAND HCT(®) (candesartan cilexetil-hydrochlorothiazide [CAN-HCTZ]) combines an angiotensin II receptor (type AT1) antagonist and a diuretic. Quantification of CAN and HCTZ in biological matrices has traditionally been difficult - developing a single method with the desired sensitivity has been the issue. RESULTS: A high-throughput bioanalytical method for the analysis of CAN and HCTZ in human plasma using liquid-liquid extraction and LC coupled to negative ion mode MS/MS has been developed and validated according to US FDA guidelines. The method uses 100 µl plasma and covers the calibration range 1-160 ng/ml for CAN and 2-160 ng/ml for HCTZ for routine pharmacokinetic studies in humans. The intra- and inter-day precision values for CAN and HCTZ met the acceptance criteria. CAN and HCTZ were stable in a battery of stability studies (benchtop, autosampler and long-term). CONCLUSION: The advantages of the described technique included a single method with a shorter run time (2.5 min), simple extraction technique, LLOQ of 1 ng/ml for CAN and 2 ng/ml for HCTZ and lower sample volume (0.10 ml), which overcomes drawbacks of two single methods for each analyte, such as higher analysis time, LOQ and sample volume, as in previously published methods. The developed assay was applied to an oral pharmacokinetic study in humans.