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The relationship between paroxetine and the sparteine oxidation polymorphism
Author(s) -
Sindrup Søren H,
Brøsen Kim,
Gram Lars F,
Hallas Jesper,
Skjelbo Erik,
Allen Ann,
Allen Graham D,
Cooper Steven M,
Mellows Graham,
Tasker Tim C G,
Zussman Barry D
Publication year - 1992
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1992.23
Subject(s) - sparteine , paroxetine , pharmacokinetics , debrisoquine , pharmacogenetics , pharmacology , endocrinology , metabolism , chemistry , medicine , cyp2d6 , serotonin , biochemistry , genotype , cytochrome p450 , receptor , organic chemistry , gene
The relationship between the selective serotonin reuptake inhibitor paroxetine and the sparteine oxidation polymorphism was investigated in a combined single‐dose (30 mg) and steady‐state (30 mg/day for 2 weeks) study including a panel of nine extensive metabolizers and eight poor metabolizers of sparteine. The median area under the plasma concentration‐time curve (AUC) after the first paroxetine dose was about seven times higher in poor metabolizers than in extensive metabolizers (3910 versus 550 nmol · hr/L), whereas at steady state the median AUC ss t interphenotype difference was only twofold (4410 versus 2550 nmol · hr/L). Plasma half‐life and steady‐state plasma concentration were significantly longer and higher, respectively, in poor metabolizers than in extensive metabolizers (41 versus 16 hours and 151 versus 81 nmol/L). Paroxetine pharmacokinetics were linear in poor metabolizers and nonlinear only in extensive metabolizers. Sparteine metabolic ratio (MR = 12 hour urinary ratio of sparteine/de‐hydrosparteine), increased during treatment with paroxetine in subjects who were extensive metabolizers, and after 14 days treatment two extensive metabolizers were phenotyped as poor metabolizers and the remaining extensive metabolizers were changed into extremely slow extensive metabolizers with sparteine MRs of 5.7 to 16.5. The inhibition of sparteine metabolism was rapidly reversed after cessation of paroxetine administration. In the poor metabolizers there were no significant changes in MRs during the study. It is concluded that paroxetine and sparteine metabolism cosegregates, but the interphenotype difference in metabolism was less prominent at steady state than after a single dose, presumably because of saturation of the sparteine oxygenase (CYP2D6) in subjects who were extensive metabolizers. Paroxetine is a potent inhibitor of sparteine oxidation by CYP2D6 in vivo. Clinical Pharmacology and Therapeutics (1992) 51, 278–287; doi: 10.1038/clpt.1992.23