In the treatment of HIV infection, a combination of anti-HIV drugs is commonly used in highly active antiretroviral therapy (HAART). One such combination recommended for clinical therapy consists of the two HIV protease inhibitors atazanavir and ritonavir and the HIV nucleotide reverse transcriptase inhibitor tenofovir. The detection of plasma and cell drug concentrations provides an assessment of actual drug exposure and patient compliance. We thus developed a simple, efficient, and sensitive method to simultaneously extract and detect these three drugs in plasma and peripheral blood mononuclear cells. The use of a liquid-liquid extraction followed by protein precipitation provided a simple process, yielding a high recovery rate for all three drugs in plasma (>92%) and in cells (>86%). The liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was able to detect 0.01, 0.25, and 2.5 pg (2, 50, and 500 pg/ml, respectively) in 5 l for atazanavir, ritonavir, and tenofovir, respectively. Validation of the method exhibited high precision and accuracy. This method was subsequently applied to a primate study to determine the concentrations of all three drugs in both plasma and cell samples. This validated method can be useful for an evaluation of drug concentrations in biological samples in an efficient and sensitive manner.
Since the introduction of highly active antiretroviral therapy (HAART) in the 1990s, the outcome in terms of life expectancy for people suffering from human immunodeficiency virus (HIV) has greatly improved due to the plasma virus load reduction to below-detectable levels (1, 2). ART treatment usually includes two or three anti-HIV drugs from different drug classes targeting different viral proteins in order to increase efficacy and lower the risk of the virus developing resistance to the treatment. A common drug combination is a nucleoside or nucleotide reverse transcriptase inhibitor (NRTI or NtRTI, respectively) with a nonnucleoside reverse transcriptase inhibitor (NNRTI) or with one or more protease inhibitors (PIs) (3).One of the first-line therapies recommended for ART-naive people is the combination of atazanavir (ATZ), ritonavir (RTV), and tenofovir (TFV) (3). ATZ is a commonly used PI that exhibits 10-to 100-fold higher antiviral potency than that of other PIs, including nelfinavir or indinavir, and demonstrates a lower rate of viral drug resistance (4-9). ATZ is typically used in combination with RTV, another PI, which inhibits the cytochrome P450 3A isoenzyme (CYP3A) metabolism of ATZ, thereby boosting ATZ exposure. RTV has also been shown to inhibit drug efflux transport by P-glycoprotein (PgP) and therefore might enhance the cellular retention of other PIs (10). TFV is a nucleotide reverse transcriptase inhibitor (NtRTI) clinically administered as tenofovir disoproxil fumarate (TDF), an oral prodrug that increases absorption and is readily hydrolyzed to the TFV active form (11). While a number of bioanalytical assays have been developed for the three drugs, they are often time...