Simultaneous Quantification of Bictegravir and Emtricitabine Using a Simple and Economical Liquid Chromatography–Ultraviolet Method for Therapeutic Drug Monitoring in Patients with Human Immunodeficiency Virus

Background: Biktarvy is an effective antiviral drug for patients with HIV. However, owing to its long-term use and poor patient adherence, sustained and effective Biktarvy treatment is consistently limited by insufficient in vivo drug concentrations. Liquid chromatography (LC)–tandem mass spectrometry–based therapeutic drug monitoring is a common tool for identifying inadequate dosages and preventing antiviral failure. However, this tool requires expensive instruments and reagents, which is a major limitation in resource-limited regions. Methods: A simple and economical liquid chromatography–ultraviolet method was established and validated for simultaneous quantification of Biktarvy-derived bictegravir (BIC) and emtricitabine (FTC) in human plasma. The samples were pretreated through protein precipitation with acetonitrile, and chromatographic separation was performed on a C18 analytical column with gradient elution at a flow rate of 1.0 mL/min. The total runtime for each sample was 15.0 minutes. Results: The method exhibited good linearity within the range of 0.5–20.0 mcg/mL for both BIC and FTC. The selectivity, lower limit of quantification, specificity, precision, accuracy, recovery, stability, and dilution integrity were validated, and all satisfied the requirements of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use: Bioanalytical method validation and study sample analysis (2022 edition) and the Chinese Pharmacopoeia for bioanalytical method validation (2015 edition). Furthermore, the method exhibited satisfactory performance, with BIC and FTC concentrations ranging between 0.80 and 6.99 mcg/mL and 0.53–4.57 mcg/mL, respectively. Conclusions: A simple and economical liquid chromatography–ultraviolet method was successfully developed for simultaneous quantification of BIC and FTC in human plasma. This method can be extensively used in therapeutic drug monitoring , as in the case of MS-based instrumental deficiency or damage, and in pharmacokinetic studies.