A new sensitive cartridge-RIA method for determination of stavudine (D4T) triphosphate in human cells in vivo.

We describe a simple and sensitive method to determine stavudine triphosphate, the active intracellular anabolite of stavudine (D4T). Quantification of D4T triphosphate was performed with a combined cartridge-radioimmunoassay (cartridge-RIA) which enabled us to measure concentrations of D4T triphosphate as low as 0.5 ng/ml, or an intracellular concentration which corresponds to 20 fmol/10(6) cells if diluted like our previously published zidovudine (ZDV) assay. The only alternate methodology at present employs liquid chromatography mass spectroscopy (LC-MS/MS). The use of the cartridge-RIA methodology provides a cost-effective alternative for the determination of in vivo cellular pharmacokinetics studies of D4T in human immunodeficiency virus (HIV)-infected persons.