title: Simultaneous determination of prednisolone, prednisone, cortisol, and cortisone in plasma by GC-MS: estimating unbound prednisolone concentration in patients with nephrotic syndrome during oral prednisolone therapy.
abstract: Individual variability of the pharmacokinetics of prednisolone based on the unbound concentration in plasma is of significant clinical consideration. The unbound concentrations of prednisolone were measured in 10 patients with nephrotic syndrome, two patients with systemic lupus erythematosus, and one patient with dermatomyositis by examining protein bindings of prednisolone on one or more occasions during prednisolone treatment. In this study, plasma concentrations of prednisolone, prednisone, cortisol, and cortisone were simultaneously analyzed by GC-MS by using stable isotope-labeled internal standards. Equilibrium dialysis was employed to accurately estimate the unbound fractions of prednisolone in plasma. The unbound fraction of prednisolone changed depending on plasma total prednisolone concentration and plasma albumin concentration. The unbound fraction of prednisolone (Y) is calculated: Y=(-0.0101x' + 0.0736) x + 10.23, where x' is the plasma albumin concentration and x is the total prednisolone concentration. The estimated concentrations of unbound prednisolone by using the above equation were in good agreement with the measured concentrations of unbound prednisolone. Since the protein binding of prednisolone did not change in the presence of prednisone (114.0 ng/ml), it appeared that prednisone produced from the therapeutic dose of prednisolone did not affect the unbound fraction of prednisolone.
authors.affiliation: Department of Medicinal Chemistry and Clinical Pharmacy, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan. sibasaki@ps.toyaku.ac.jp
authors.forename: Hiromi
authors.initials: H
authors.lastname: Shibasaki
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nakayama
authors.forename: Takashi
authors.initials: T
authors.lastname: Furuta
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Kasuya
authors.forename: Mari
authors.initials: M
authors.lastname: Tsuchiya
authors.forename: Akinori
authors.initials: A
authors.lastname: Soejima
authors.forename: Akira
authors.initials: A
authors.lastname: Yamada
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Nagasawa
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D003348:Cortisone / Q000097:blood* / Q000737:chemistry; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D009404:Nephrotic Syndrome / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy*; D011239:Prednisolone / Q000008:administration & dosage / Q000097:blood* / Q000737:chemistry / Q000627:therapeutic use; D011241:Prednisone / Q000097:blood* / Q000737:chemistry
chemical_list: D011239:Prednisolone; D003348:Cortisone; D011241:Prednisone; D006854:Hydrocortisone