A multiple reaction monitoring liquid chromatography – mass spectrometry method for the simultaneous determination of five antiretroviral drugs in human blood plasma.
14We have discerned some characteristics of protonated and sodiated forms of emtricitabine 15 tenofovir and tenofovir disoproxil fumarate in aqueous solutions using mass spectrometry/mass 16 spectrometry (MS/MS), nuclear magnetic resonancespectroscopy (NMR) and Ab 17 initiocalculations. Protonated species exhibited different mass spectral characteristics from 18 sodiated species for the three antiretroviral drugs. Sodiation of the three compounds yields 19 extremely stable conformers which require high excitation energies to detach the sodium cation 20 using MS/MS. In the case of emtricitabine (FTC), collision induced dissociation (CID) of the 21 protonated species with m/z 248 yieldedm/z 130 as the major product ion by losing 2-ethyl-1,3-22 oxathiolane. MS/MS of the sodiated molecular ion [M+Na] + with m/z 270 would be expected to 23 yield [M+H] + i.e. m/z 248 by losing the Na + cation but instead lost 2-ethyl-1,3-oxathiolane and 24 left the Na + cation well sequestered within the ionic complex.Similar observations were made 25with tenofovir disoproxil fumarate (TDF) and tenofovir (TFV). Ab initio calculations showed in 26 the case of sodiated TDF and TFV that, the sodium could only be cleaved when a nucleophilic 27 species i.e. PO 2 to which it was coordinated to, fragmented requiring activation energy of 1.5 eV. 28 The potential energy barrier to remove the Na + cation alone was too high to allow the cleavage to 29 proceed. NMR data showed that when TFV or TDF coordinates with Na + ions at one of the 30 nitrogens at position 1 in the purine moiety of the molecule, it also interacts with oxygens of the 31 phospho group to form an ionic complex and perturbs the chemical environments of several 32 atoms in the periphery. The abundance of sodium cations and their strong interactions with the 33 core structures of FTC, TDF and TFV make sodiated species as the best candidates for their 34 quantitationusing MS/MSespecially in biological fluids. Evidence for improved sensitivity when 35 sodiated species of some of the antiretroviral (ARV) drugs were used for quantitation exists in 36 the literature. 37 2 1 1. Introduction 2Truvada® is a combination of emtricitabine (FTC) and tenofovirdisoproxil fumarate (TDF) 3 and is a nucleoside analog reverse transcriptase inhibitor (NRTI) used for treating HIV-1 in 4 adults and children of age 12 years and above. It contains two drugs and thus can be classified as 5 combination therapy. Dueto its widespread use, it is important to understand the behavior of the 6 individual components of the drug in vitro for purposes of following their fate in humans, the 7 environment in general and also for unravelling critical information necessary to develop 8 accurate and sensitive methods for their detection. Toxicologists in areas such as forensic and 9 analytical sciences may also derive interest in the behavior of thedrugs in humans and the 10 environment. Many analytical methods for the determination of the individual drug components 11 of Truvada® i.e. FTC and TDF have been de...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.