Determination of zidovudine/lamivudine/nevirapine in human plasma using ion-pair HPLC

A new high-performance liquid chromatography (HPLC) assay was developed for the simultaneous determination of zidovudine (AZT)/lamivudine (3TC)/nevirapine in human plasma. Plasma samples were treated using a solid-phase extraction procedure. The compounds were separated using a mobile phase of 20 mM sodium phosphate buffer (containing 8 mM 1-octanesulfonic acid sodium salt)-acetonitrile (86:14, v/v) with pH adjusted to 3.2 with phosphoric acid on an octylsilane column (150x3.9 mm i.d.) with UV detection at 265 nm. Aprobarbital was chosen as the internal standard (IS). The method was validated over the range of 57.6-2880 ng/ml for AZT, 59.0-17650 ng/ml for 3TC and 53.2-13300 ng/ml for nevirapine. The method was shown to be accurate, with intra-day and inter-day accuracy from 0.1 to 11% and precise, with intra-day and inter-day precision from 0.4 to 14%. Extraction recoveries of the analytes and IS from plasma were higher than 92%. The assay should be suitable for use in pharmacokinetic studies and routine plasma monitoring of this triple-drug therapy in AIDS patients.