Abstract
High performance liquid chromatography (HPLC) with a fluorometric detector was applied to the determination of propranolol and its major metabolite, naphthoxylactic acid (NLA), in human plasma following a single oral low dose (20 mg) of propra olol HCl. Propranolol and NLA were extracted successively from the sample aliquot. The carboxyl group of NLA was methylated with diazomethane in order to avaoid interference from blank plasma and a very strongly tailing peak on the HPLC chromatogram. The mean recoveries of propranolol and NLA subjected to the entire analytical protocol were better than 92%. The detection limits were 0.5 ng/ml for propranolol and 2 ng/ml for NLA. The calibration curves for propranolol HCl (20-100 ng/ml) and NLA (0.2-2 μg/ml), showed good linearity. The plasma concentrations of propranolol and NLA following a single oral administration of 20 mg of propranolol HCl to three healthy male subjects were determined by this method.
