UPLC–MS/MS quantification of nanoformulated ritonavir, indinavir, atazanavir, and efavirenz in mouse serum and tissues

Animal pharmacokinetic and tissue distribution assays of antiretroviral therapeutic drugs require accurate drug quantification in biological fluids and tissues. Here we report a simple, rapid, and sensitive ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method for quantification of commonly used antiretroviral drugs ritonavir (RTV), indinavir (IDV), atazanavir (ATV), and efavirenz (EFV) in mouse serum and tissues (liver, kidney, lung, and spleen). These antiretroviral drugs are currently the cornerstones of common therapeutic regimens for human immunodeficiency virus (HIV) infection. Chromatographic separation was achieved using a gradient mobile phase (5% acetonitrile in methanol and 7.5 mM ammonium acetate (pH 4.0)) on an ACQUITY UPLC®BEH Shield RP 18 column. All compounds eluted within a 7 min run time. Lopinavir was used as an internal standard. Detection was achieved by dual positive and negative ionization modes on a quadrupole linear ion trap hybrid mass spectrometer with an electrospray ionization (ESI) source. The dynamic range was 0.2–1000 ng/mL for RTV, IDV, and ATV, and 0.5–1000 for EFV. The method was validated and showed high and consistent intra-day and inter-day accuracy and precision for all analytes. This method is used to support the preclinical development studies of targeted- and sustained-release combination ART (nanoART). The current data demonstrate a 1.5–4 fold increase in serum and tissue AUC of nanoformulated ATV, RTV, and EFV administered to mice when compared to native drug. In addition, the tested formulation enhanced exposure of the same anti-HIV drugs in mouse tissues.