A rapid and sensitive method for simultaneous determination of lamivudine and zidovudine in human serum by on‐line solid‐phase extraction coupled to liquid chromatography/tandem mass spectrometry detection

Abstract

A method based on solid-phase extraction (SPE) coupled to high-performance liquid chromatography (HPLC) with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection was developed for the simultaneous determination of lamivudine (3TC) and zidovudine (AZT) in human serum, using didanosine (ddI) as internal standard. The acquisition was performed in multiple reaction monitoring (MRM) mode, monitoring the transitions m/z 230.0 --> 111.8 for 3TC, m/z 268.1 --> 126.8 for AZT, and m/z 237.2 --> 136.8 for ddI. The limits of detection and quantitation were 3 and 10 ng/mL for 3TC, and 5 and 15 ng/mL for AZT. The method was linear in the studied ranges (10-1500 ng/mL for 3TC and 15-3000 ng/mL for AZT), with r(2) > 0.99 for each drug, and the run time was 4 min. The intra-assay precisions (%) were in the ranges 1.9-8.7 (3TC) and 2.2-8.9 (AZT), the inter-assay precisions were in the ranges 2.6-9.0 (3TC) and 4.2-8.1 (AZT), and the intra- and inter-assay accuracies were >97% for both drugs. The absolute recoveries were 95-99% for 3TC (45, 600 and 1200 ng/mL) and 104-112% for AZT (45, 1000 and 2400 ng/mL). The analytical method was applied to a bioequivalence study in which 24 healthy adult volunteers received single oral doses of the reference formulation and two test combined AZT/3TC tablets, in an open, three-period, balanced, randomized, crossover protocol. Based on the 90% confidence interval of the individual ratios (test formulation/reference formulation) for C(max) (peak serum concentration) and AUC(0-inf) (extrapolated area under the serum concentration vs. time curve from time zero to infinity), it was concluded that the two test formulations are bioequivalent to the reference formulation with respect to the rate and extent of absorption of both 3TC and AZT.

Absence of a Universal Mechanism of Mitochondrial Toxicity by Nucleoside Analogs

“…Drug stocks were stored at Ϫ20°C between doses, and new stocks were prepared before each experiment. The doses of AZT and ddI were selected to represent steady-state peak plasma levels of patients receiving NRTI therapy (17,38), as well as a supratherapeutic dose to observe concentrationrelated effects; supratherapeutic doses of ddC were used after preliminary experiments showed minimal toxicity with ddC in H9c2 cells. Additionally, another treatment group containing 0.5 g/ml (1.3 M) EtBr was included as a positive control.…”

Extraction en phase solide de 22 médicaments d'intérêt en toxicologie médico-légale

“…De nombreux protocoles sont publiés pour chacune de ces cartouches, ils ont servi de base à nos travaux [7][8][9][10][11][12][13][14][15][16].…”

“…Chaque étape de l'extraction a été améliorée individuellement [7,12,13,15]. Les phases de lavage et d'élution ont éga-lement été étudiées afin de minimiser les pertes de molécules d'intérêt et pour maximiser la récupération des molécules adsorbées sur la phase de la colonne.…”

“…tableau III). Chaque étape a été testée en terme de composition et de volume de solvants [7,12,13,15]. Ont également été optimisées préalable-ment à l'extraction, la préparation du sang (dilution, choix du pH et de la composition de la solution tampon, centrifugation), et postérieurement à l'extraction, la préparation de l'échan-tillon à injecter (évaporation de l'extrait, flaconnage, mise en solution).…”

Identifying bacterial species using CE–MS and SEQUEST with an empirical scoring function

“…MALDI and ESI-MS have both been employed to analyze microorganisms [7][8][9]. ESI-MS combines on-line detection with sample purification, concentration and separation methods, including microdialysis, SPE, LC and CE [10][11][12][13]. Therefore, ESI-MS provides the ability of analyzing complex systems.…”