Stereoselective disposition of talinolol in man.
The disposition of the beta-blocking drug talinolol is controlled by P-glycoprotein in man. Because talinolol is marketed as a racemate, we reevaluated the serum-concentration time profiles of talinolol of a previously published study with single intravenous (30 mg) and repeated oral talinolol (100 mg for 14 days) before and after comedication of rifampicin (600 mg per day for 9 days) in eight male healthy volunteers (age 22-26 years, body weight 67-84 kg) with respect to differences in the kinetic profiles of the two enantiomers S(-) talinolol and R(+) talinolol. Additionally, the metabolism of talinolol in human liver microsomes was examined. After oral administration, S(-) talinolol was slightly less absorbed and faster eliminated than R(+) talinolol. The absolute bioavailabilty of the R(+) enantiomer of talinolol was slightly but significantly higher than of its S(-) enantiomer. Coadministration of rifampicin further intensified this difference in the disposition of R(+) and S(-) talinolol (p < 0.05). Formation of 4-trans hydroxytalinolol was the major metabolic pathway in human liver microsomes. All Cl(int) values of S(-) were higher than of R(+) talinolol; 0.1 microM ketoconazole inhibited the formation of all metabolites. In conclusion, the stereoselectivity of talinolol disposition is of minor importance, and most likely caused by presystemic biotransformation via CYP3A4. The less active R(+) talinolol might be suitable for phenotyping P-glycoprotein expression in man.
Zschiesche
Michael
M
Department of Pharmacology, Ernst Moritz Arndt University, Friedrich Loeffler Strasse 23d, D-17487 Greifswald, Germany.
Lemma
Girum Lakew
GL
Klebingat
Klaus-Jürgen
KJ
Franke
Gerd
G
Terhaag
Bernd
B
Hoffmann
Anna
A
Gramatté
Thomas
T
Kroemer
Heyo K
HK
Siegmund
Werner
W
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis; D000319:Adrenergic beta-Antagonists / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics*; D000328:Adult; D019540:Area Under Curve; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D008968:Molecular Conformation; D011412:Propanolamines / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics*; D012293:Rifampin / Q000493:pharmacokinetics; D018709:Statistics, Nonparametric
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000319:Adrenergic beta-Antagonists; D004791:Enzyme Inhibitors; D011412:Propanolamines; C011550:talinolol; D012293:Rifampin