Liquid chromatographic–tandem mass spectrometric assay for the simultaneous determination of didanosine and stavudine in human plasma, bronchoalveolar lavage fluid, alveolar cells, peripheral blood mononuclear cells, seminal plasma, cerebrospinal fluid an

We have developed a sensitive, high-pressure liquid chromatographic–tandem mass spectrometric (LC/MS/MS) method for the simultaneous determination of didanosine (ddI) and stavudine (d4T) in human plasma, bronchoalveolar lavage fluid (BALF), alveolar cells (AC), peripheral blood mononuclear cells (PBMC), seminal plasma, cerebrospinal fluid (CSF), and tonsil tissue. Plasma, AC, PBMC and CSF were run with an isocratic HPLC method, while BALF supernatant, semen, and tonsil tissue utilized a gradient elution. Samples were prepared by solid phase extraction. Detection was by electrospray positive ionization with multiple reaction monitoring mode. The lower limits of quantitation for both ddI and d4T were 2.0 ng/ml in plasma; 0.5 ng/ml in CSF; 0.4 ng/ml in AC, PBMC, and BALF; 1.0 ng/ml in seminal plasma; and 0.01 ng/mg in tonsil tissue.