Navuridine

Zidovudine (AZT) therapy given during pregnancy has been shown to reduce the vertical transmission of the human immunodeficiency virus (HIV) from mother to fetus. In order to investigate the efficacy of AZT, it is important to know the concentration of its active phosphorylated metabolites. We have developed the first CE method for the simultaneous quantitation of AZT and zidovudine monophosphate (AZT‐MP) from rat plasma, amniotic fluid and fetal tissues. Sample extractions were performed by protein precipitation using acetonitrile for the plasma and amniotic fluids, while in fetal tissues solid phase extraction using Waters Oasis™ HLB extraction cartridges was used. Recoveries ranged from 78 to 92% for AZT, AZT‐MP and 3′‐azidouridine (internal standard, AZDU), in the three matrices. The optimum separation conditions were achieved using a 40 mm sodium dodecylsulfate (SDS) in 50 mm phosphate buffer (pH 7) with a run voltage of 15 kV. The CE system consists of a 75 µm i.d., 50 cm effective length uncoated fused silica capillary. The method was validated over the range 0.5–100 µg/ml (µg/g for tissues). Intra‐day precision (RSD) and accuracy (%error) for AZT ranged from 0.13 to 11 and 0.68 to 11.1%, respectively, while for AZT‐MP it ranged from 2.05 to 11.1 and 4.22 to 11.7%. Inter‐day precision and accuracy for AZT ranged from 3.82 to 11.2 and 3.14 to 9.01%, while for AZT‐MP it ranged from 3.9 to 9.32 and 3.44 to 9.37%, respectively. We also report the enzymatic dephosphorylation of AZT‐MP in the placental tissue of rats. This new enzymatic pathway provides increased understanding of the mechanism of anti‐viral transport in the rat during pregnancy. Copyright © 2004 John Wiley & Sons, Ltd.

A rapid and efficient high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method for the determination of concentrations of the carbocyclic nucleoside antiviral Abacavir in maternal rat plasma, amniotic fluid, placental and fetal tissue samples has been developed and validated. All tissue samples were homogenized in water prior to analysis and all samples were prepared by acetonitrile precipitation followed by dilution with HPLC‐grade water. Separation of the analyte and internal standard from the matrices was achieved on a C8 analytical column (2.1 × 150 mm, 5 μm particle size). The mobile phase consisted of 10 mM ammonium acetate/acetonitrile using a gradient method at a flow rate of 0.25 mL/min for all matrices. The method yields retention times of approximately 3.4 and 5.1 min for the internal standard (Azidouridine) and Abacavir, respectively. For all matrices the limit of detection was approximately 1 ng/ml. Recoveries from the different matrices ranged from 53–87% for Abacavir and from 69–84% for Azidouridine. Within‐ and between‐run precision (%RSD) and accuracy (%Error) were under 15% for all matrices. Copyright © 2004 John Wiley & Sons, Ltd.