High-performance liquid chromatographic assay and preclinical pharmacological studies of pibenzimol (bisbenzimidazole).

A sensitive and selective high-performance liquid chromatographic assay with ultraviolet or fluorescence detection has been developed for the experimental antitumor agent pibenzimol. Drug is isolated from plasma or other aqueous solutions with reversed-phase C18 disposable extraction columns and chromatography afforded with a deactivated reversed-phase C18 column and phosphate buffer--methanol mobile phase. Plasma standard curves are linear for concentrations for pibenzimol from 0.01 to 5.0 micrograms/ml. Pibenzimol is stable in fresh human plasma and whole blood. Pibenzimol appears to bind to plasma proteins; however, drug adsorption to glass, plastic, membranes, and filters precludes accurate determination of pibenzimol plasma protein binding. Plasma concentrations of pibenzimol fall rapidly following rapid intravenous administration to rabbits, but parent drug is detectable in plasma 24 h after drug administration. The 24-h urinary recovery of pibenzimol is 10-20%.