title: Quantification of clomiphene metabolite isomers in human plasma by rapid-resolution liquid chromatography-electrospray ionization-tandem mass spectrometry.
abstract: Since the 1960s, clomiphene citrate is used for ovulation induction. Since nonresponse to clomiphene therapy is still not well understood, interindividual variability of clomiphene metabolism has been considered to be a plausible explanation. Therefore, a comprehensive, rapid, sensitive, and specific analytical method for the quantification of (E)- and (Z)-isomers of clomiphene and their putative N-desethyl, N,N-didesethyl, 4-hydroxy, and 4-hydroxy-N-desethyl metabolites, and the N-oxides in human plasma has been newly developed, using HPLC-tandem mass spectrometry and stable isotope-labeled internal standards. All standards other than the parent drug were synthesized in our laboratory. Following protein precipitation analytes were separated on a ZORBAX Eclipse plus C18 1.8 μm column with a gradient of 0.1% formic acid in water and 0.1% formic acid in acetonitrile and detected on a triple quadrupole mass spectrometer with positive electrospray ionization in the multiple reaction monitoring mode. Lower limit of quantification for metabolites ranged from 0.06 ng/mL for clomiphene-N-oxides to 0.3 ng/mL for (E)-N-desethylclomiphene. The assay was validated according to FDA guidelines. Plasma levels of clomiphene and its metabolites were measured in two women after single-dose treatment with clomiphene.
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tübingen, Stuttgart, Germany.
authors.forename: Boian
authors.initials: B
authors.lastname: Ganchev
authors.forename: Georg
authors.initials: G
authors.lastname: Heinkele
authors.forename: Reinhold
authors.initials: R
authors.lastname: Kerb
authors.forename: Matthias
authors.initials: M
authors.lastname: Schwab
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Mürdter
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D002996:Clomiphene / Q000097:blood* / Q000378:metabolism; D005260:Female; D006801:Humans; D007536:Isomerism; D020845:Selective Estrogen Receptor Modulators; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D020845:Selective Estrogen Receptor Modulators; D002996:Clomiphene