Simultaneous HPLC determination of isoniazid and acetylisoniazid in plasma

A rapid and simple high-performance liquid chromatographic method has been developed for simultaneous determination of isoniazid (INH) and acetylisoniazid (AcINH) in microsamples of plasma. Plasma samples were deproteinated by addition of trichloroacetic acid, and the drug and its metabolite were then separated by reversed-phase HPLC on an octadecylsilane-bonded silica column. The mobile phase was a gradient prepared from an aqueous solution of 1-hexanesulfonic acid sodium salt (pH 3) and acetonitrile. The effluent was monitored by UV detection at 290 nm. Calibration plots were linear in the range 0.5 to 15.0 μg mL -1 and the limit of quantification was 0.5 μg mL-1 for both drugs. The lower limits of detection for INH and AcINH were 0.24 and 0.12 μg mL-1, respectively. Results from analysis of quality-control samples at concentrations of 0.8, 5, and 13 μg mL-1 were indicative of good repeatability and precision. Recovery from plasma was 64%25 for INH and 55%25 for AcINH. INH was more stable than AcINH in plasma at -80°C.

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