title: Determination of betaxolol and its metabolites in blood and urine by high-performance liquid chromatography with fluorimetric detection.
abstract: Analytical methods for the determination of betaxolol and two of its metabolites in blood and urine are described. Betaxolol, alpha-hydroxybetaxolol, and the acid metabolite were extracted, with over 65% efficiency, from biological samples by liquid-liquid extraction methods. Analysis was performed using reversed-phase high-performance liquid chromatography with fluorimetric detection. N,N-Dimethyloctylamine (0.005 M) was used to improve the chromatography of betaxolol and alpha-hydroxybetaxolol, while acetic acid (1%) was used for the acid metabolite. An excitation wavelength of 200 nm was found to produce the best detector response. Linear standard curves were obtained for all three compounds with detection limits (signal-to-noise ratio = 3) varying between 1 and 10 ng/ml. The coefficients of variation of the determination for all three compounds in blood and urine varied between 3.0 and 8.7%. The metabolism of betaxolol was studied in twelve healthy male subjects. The amounts (mean +/- S.D.) of betaxolol, alpha-hydroxybetaxolol and the acid metabolite renally excreted in the first 48 h after intravenous administration of 10 mg of betaxolol hydrochloride are 17.1 +/- 6.2, 0.4 +/- 0.1 and 14.5 +/- 3.7%, respectively, of the administered dose.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284.
authors.forename: Y W
authors.initials: YW
authors.lastname: Wong
authors.forename: T M
authors.initials: TM
authors.lastname: Ludden
mesh_terms: D000328:Adult; D015784:Betaxolol / Q000031:analogs & derivatives / Q000097:blood* / Q000378:metabolism / Q000652:urine*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D008297:Male; D013050:Spectrometry, Fluorescence
chemical_list: C068931:alpha-hydroxybetaxolol; D015784:Betaxolol