Liquid chromatographic analysis of enviradene, a new antiviral agent, in plasma and its application in bioavailability studies in the dog.

A rapid and specific high-performance liquid chromatographic (HPLC) assay has been developed for the determination of enviradene, 1, at concentrations of 2-5 ng/mL in plasma. The drug was extracted from the samples using benzene. The benzene extract was evaporated and the residue dissolved in the mobile phase. The HPLC system consisted of a reversed-phase column and a 75% methanol:25% 0.2 M sodium acetate mobile phase. Either a UV detector set at 268 nm or an electrochemical (EC) detector set at a potential of +0.9 V (versus Ag/AgCl/3 M NaCl) was used to monitor the drug. A column-switching system was used to remove late-eluting plasma constituents that interfered in subsequent chromatograms. The limit of sensitivity was 2 ng/mL for the HPLC-EC procedure and 5 ng/mL for the HPLC-UV procedure. Recovery from plasma was approximately 97%; the procedure had a relative error of approximately 3% and a relative standard deviation of 4.5% over the range of 20-200 ng of 1/mL of plasma. Following intravenous administration of 1 or 2 mg/kg of 1 to dogs, the parent drug was quantitated in plasma for 24 h using this procedure. The terminal phase half-life in plasma was calculated to be 10 h. Oral administration to dogs of single 8 mg/kg doses of 1, formulated with povidone-30 or polysorbate 80 and microcrystalline cellulose, produced high and persistent plasma concentrations of drug. At doses below 2 mg/kg, plasma concentrations were found to be nonlinearly related to the amount of the dose administered. The bioavailability of the drug in dogs was found to be increased by the concomitant administration of food.