title: Pharmacokinetic parameters of sulfated tibolone metabolites in postmenopausal women after single and multiple doses of tibolone.
abstract: The objective of this study was to determine pharmacokinetic parameters of sulfated tibolone metabolites after single dose and their accumulation after multiple doses of tibolone. Blood samples from postmenopausal women in a single-dose (2.5 mg tibolone), open-label study (n=8) and multiple-dose (placebo, 0.3, 0.625, 1.25, or 2.5 mg/day tibolone for twenty-six cycles of 28 days), randomized, double-blind study (n=15) were analyzed for non-sulfated and sulfated tibolone metabolites by validated gas chromatography-mass spectrometry (GC-MS) and liquid chromatography with tanolam mass spectrometry (LC-MS/MS), respectively. The predominant non-sulfated and sulfated metabolites after a single dose were 3alpha-hydroxy-tibolone and 3alpha,17beta-di-sulfated (di-S)-tibolone. At 3 h, >90% of metabolites were sulfated. Tibolone and Delta(4)-tibolone were detectable for about 6 h. After multiple treatment cycles with different doses, metabolite levels at 10 h were dose-related and levels of di-S metabolites were three- to fivefold higher than after a single dose. Tibolone metabolite levels did not differ between cycles. Inactive di-S tibolone metabolites predominated in blood. No accumulation occurred between cycles 7 and 26.
authors.affiliation: NV Organon, Global Venture Team Livial, Oss, The Netherlands. herman.verheul@organon.com
authors.forename: H A M
authors.initials: HA
authors.lastname: Verheul
authors.forename: C J
authors.initials: CJ
authors.lastname: Timmer
authors.forename: H J
authors.initials: HJ
authors.lastname: Kloosterboer
mesh_terms: D001711:Biotransformation; D004311:Double-Blind Method; D004492:Edetic Acid / Q000378:metabolism; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006900:Hydroxylation; D008875:Middle Aged; D009652:Norpregnenes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D017698:Postmenopause / Q000378:metabolism*; D020845:Selective Estrogen Receptor Modulators / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013431:Sulfates / Q000378:metabolism
chemical_list: D009652:Norpregnenes; D020845:Selective Estrogen Receptor Modulators; D013431:Sulfates; D004492:Edetic Acid; C027385:tibolone