Bioanalytical Method Validation for the Determination of Warfarin in Spiked-Saliva Using Fluorometric HPLC for TDM Application

Abstract

Saliva becomes an alternative biological matrix for therapeutic drug monitoring (TDM) application since there is a strong correlation between warfarin plasma concentration and saliva; further, the sampling is non-invasive and more comply with pediatric and geriatric patients. This study aims to validate the parameters of the warfarin bioanalytical method in spiked-saliva according to the criteria from the Food and Drug Administration (FDA) in the Guidance for Industry Bioanalytical Method Validation. The method used is Fluorometric HPLC with an excitation wavelength of 310 nm and an emission wavelength of 390 nm. The mobile phase involved is phosphate buffer-methanol, and the stationary phase is C18. The LoD and LoQ obtained are 0.71 ng/mL and 2.16 ng/mL, respectively. The coefficient of variation and %diff in the selectivity, accuracy, and precision parameters have met the criteria of the bioanalytical method of less than 20%. Meanwhile, the average %recovery is 101.30%. To conclude, the developed warfarin bioanalytical method has fulfilled the established criteria. It can, therefore, be used to determine warfarin concentration in saliva as an alternative method for TDM services in the clinical domain.