title: Stereoselective oral bioavailability of (+/-)-propranolol in the dog. A GC-MS study using a stable isotope technique.
abstract: The disposition of (+)- and (-)-propranolol and their glucuronic acid conjugates, (+)-POG and (-)-POG, in plasma was determined in 5 dogs following single 160 mg oral doses of stable isotope labeled racemic propranolol. Each animal received one dose of the racemate with the (+)-isomer labeled with two deuteriums and one dose with the (-)-isomer labeled. The isomers were separated and measured by gas chromatography-mass spectrometry. No stable isotope effect was detected. The area under the plasma concentration - time curve (AUC) for (-)-propranolol was only 54 +/- 10 per cent (mean +/- SD; n = 10) of the AUC for (+)-propranolol. The AUC of (-)-POG exceeded the AUC of (+)-POG by 4.02 +/- 1.22 times (mean +/- SD: n = 10). The time to peak plasma concentration (3.9-4.3 hr) and the half-life (1.6-1.9 hr) were identical for both isomers of propranolol as well as of POG. These results demonstrate a significantly lower oral bioavailability of (-)- as compared to (+)-propranolol in the dog, which appears to be associated with stereoselective presystemic glucuronidation of (-)-propranolol.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D002849:Chromatography, Gas; D003903:Deuterium; D004285:Dogs; D007700:Kinetics; D008297:Male; D013058:Mass Spectrometry; D008722:Methods; D011433:Propranolol / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D013237:Stereoisomerism; D013997:Time Factors
chemical_list: D011433:Propranolol; D003903:Deuterium