title: Pharmacokinetics of oral timolol studied by mass fragmentography.
abstract: The pharmacokinetics of timolol, after oral administration of single 20 mg doses to healthy subjects, has been studied using an original electron beam ionization GLC-mass spectrometry technique with computer -- controlled multiple ion detection. This method of mass fragmentography, tested with propranolol as an internal standard, permitted the measurement of timolol concentrations as low as 1 ng/ml with good precision and accuracy. It enabled the plasma level to be followed up to the twelfth hour after treatment. Individual variation was observed in bioavailability; the peaks plasma concentration (Cmax) of 50 to 103 ng/ml being achieved at different times(0.5--3h). The residual level after 12 h differed greatly between the subjects (0.8 to 7.2 ng/ml). The mean half-life of the terminal elimination phase was 2.62 +/- 0.17 h. Extra-renal elimination (metabolic and biliary) represented the main route of elimination, with a renal to body clearance ratio of 0.123. This level paralleled the percentage of unaltered timolol excreted in urine 24 h after its administration.
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007700:Kinetics; D008297:Male; D011412:Propanolamines / Q000378:metabolism*; D013999:Timolol / Q000008:administration & dosage / Q000378:metabolism*
chemical_list: D011412:Propanolamines; D013999:Timolol