Determination of zidovudine/zalcitabine/nevirapine in human plasma by ion-pair HPLC

A novel high-performance liquid chromatography (HPLC) assay was developed f or the simultaneous determination of zidovudine (AZT)/zalcitabine (ddC)/nev irapine in human plasma. Plasma samples were treated using a solid-phase ex traction procedure. The analytes were separated using a mobile phase contai ning 20 mM sodium phosphate buffer (containing 8 mM 1-octane-sulfonic acid, sodium salt)-acetonitrile (86:14, v/v) with pH adjusted to 3.2 with phosph oric acid on an octylsilane column (150 x 3.9 mm. I.D.) with UV detection a t 265 um. Aprobarbital was chosen as internal standard. The method was vali dated over the range of 57.6-2880 ng/mL for AZT, 20.2-2020 ng/mL for ddC an d 53.2-13300 ng/mL for nevirapine. Intra-day and inter-day accuracy were le ss than 10.7% and intra-day and inter-day precision were less than 13.7%. E xtraction recoveries of all analytes from plasma were higher than 88.5%. Th e assay should be applicable for pharmacokinetic studies and routine monito ring of these drugs in plasma.