A Robust and Accurate Filter Paper–Based Dried Plasma Spot Method for Bictegravir Monitoring in HIV Therapy

Context: Therapeutic drug monitoring (TDM) involves the collection of biological samples such as blood, plasma, urine, and saliva. The most commonly used biological matrix for the detection of drugs is either blood or plasma, as they are widely accepted by the regulatory authorities. Such studies require a significant amount of blood to be collected and even more if the study is performed in a plasma sample. The growing demand to minimize the blood or biological samples required for the study of drugs, dried blood spot, or the dried plasma spot techniques has been studied by its demand. Objective: The main aim was the development of a novel method for the determination of the circulating blood plasma levels in clinical samples using spotted and dried plasma on filter paper as a substrate detection of bictegravir, an HIV integrase strand transfer inhibitor (INSTI) drug from dried plasma spots. Materials and Methods: The quantitation, as well as the detection of the plasma drug concentration, was done using liquid chromatography–tandem mass spectrometry LC-MS/MS. Sixty microliters of plasma spiked with 2% of the drug was spotted on Whatman filter paper and was left to dry at room temperature. The drug was extracted using methanol as a precipitating agent. Results: The extraction technique yielded a recovery of 100%. The assay exhibited excellent linearity in the range of 20–1200 ng/mL. Discussion and Conclusion: The method developed is a robust, simple, and accurate method to extract drug from the plasma. This method enables to produce a clean sample, proving to be cheaper and more accurate with maximum recovery.