Evaluation of Impact of Concomitant Drugs in Human Plasma on LC-MS/MS Based Quantification of Olmesartan and Hydrochlorothiazide

Liquid chromatography tandem mass spectrometer (LC-MS/MS) is an advanced analytical technique, which requires a validated method for a particular drug, prior to analysis of study samples. The analytical method must be selective with ability to distinguish between analyte of interest and endogenous or exogenous interferents (salts, proteins, lipids, metabolites, and concomitant medications). Concomitant medications are general treatment taken by subject population. Regulatory guidelines advocate evaluation of effects of co-medication on analytical methods, but detailed description of experiment designs is not yet reported. In the present study, a simple procedure to evaluate the co-medication effects on LC-MS/MS based simultaneous quantitation of Olmesartan and hydrochlorothiazide is explained. This is the first report that provides details on experimental design for assessing effects of co-medications on LC-MS/MS based quantitation of drugs in biological samples. This experimental design is likely to facilitate assessment of effect of co-medications on analytical methods applied in pharmacokinetics, drug development, and therapeutic monitoring.