DETERMINATION OF ZIDOVUDINE AND LEVOFLOXACIN IN HUMAN PLASMA BY REVERSED PHASE HPLC AND SOLID PHASE EXTRACTION

Abstract

A new high performance liquid chromatography (HPLC) assay was developed for the simultaneous determination of zidovudine (AZT) and levofloxacin in human plasma. Plasma samples were treated with a solid-phase extraction procedure. The compounds were separated using a mobile phase of 86 : 14 v/v 25 mM sodium phosphate monobasic monohydrate and 0.1% trifluoroacetic acid (pH 2.4) – acetonitrile on an octadecylsilane column (150 × 4.6 mm i.d.) with UV detection at 266 nm. Ciprofloxacin was used as the internal standard (IS). The method was validated over the range of 26.3–2600 ng/mL for AZT, and 51.2–5069 ng/mL for levofloxacin. The method proved to be accurate (percent bias for all calibration samples varied from −6.2 to 5.6%) and precise (within-run precision ranged from 0.9 to 9.7% and between-run precision ranged from 1.3 to 7.5%). The mean absolute recoveries were 94.1% for AZT, 91.2% for levofloxacin, and 84.7% for the internal standard. The assay should be suitable for use in pharmacokinetic studies and routine plasma monitoring of these drugs in HIV infected patients.