Abstract
A sensitive, specific, reproducible, and convenient high-performance liquid chromatographic (HPLC) assay was developed for quantitation of the new ultra short acting β-adrenergic antagonist, flestolol (1), in whole blood. The instability of the compound in blood was overcome by the esterase inhibitor, NaF, and deproteinization of blood samples with CH3CN:CH2CI2 (2:5). The internal standard was p-ethoxyphenethyl alcohol. The compounds were back extracted from the CH3CN:CH2CI2 phase into a small volume of pH 3–4 phosphate buffer and then separated on a reversed-phase C18 column with 0.05M phosphate buffer (pH 3–4) in acetonitrile (4.6:1) as the mobile phase, and detected with an UV detector at 229nm. The assay was linear with a blood concentration range from 10 to 1270ng/mL (r2>0.998, p>0.01), and reproducible with an overall CV of 8%. The assay procedure was used to determine the blood levels of flestolol intravenously infused into a male dog for 105min at 230 μg/kg/min. The steady-state unchanged drug concentration of 5 μMg/mL in blood was achieved within 10–20min and declined biexponentially to 0.02 μMg/mL at 6h following termination of the infusion.
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