title: Variability of cytochrome P450 1A2 activity over time in young and elderly healthy volunteers.
abstract: OBJECTIVE
  To assess the age-associated changes over time of plasma paraxanthine/caffeine (PAX/CAF) ratios used as a probe for CYP1A2 activity.
  
  
  METHODS
  Intraindividual and interindividual variabilities in PAX/CAF ratio were compared by phenotyping with caffeine, 16 young and 16 elderly healthy subjects on five occasions.
  
  
  RESULTS
  PAX/CAF ratio variability was comparable regardless of age (intraindividual CV: 17.6 +/- 6% and 16.2 +/- 5.9%, interindividual CV: 48.1 +/- 2.9% and 42.7 +/- 3.6% in young and elderly, respectively). The PAX/CAF ratio was lower in elderly than in young subjects (95% CI for the difference: 0.004, 0.32) but the difference was not significant in nonsmokers compared separately.
  
  
  CONCLUSIONS
  The variability over time of the PAX/CAF ratio is not influenced by age.
authors.affiliation: Department of Pharmacology, Saint Antoine Paris-VI University Hospital, Paris, France. Tabassome.Simon@chusa.jussieu.fr
authors.forename: T
authors.initials: T
authors.lastname: Simon
authors.forename: L
authors.initials: L
authors.lastname: Becquemont
authors.forename: B
authors.initials: B
authors.lastname: Hamon
authors.forename: E
authors.initials: E
authors.lastname: Nouyrigat
authors.forename: Y
authors.initials: Y
authors.lastname: Chodjania
authors.forename: J M
authors.initials: JM
authors.lastname: Poirier
authors.forename: C
authors.initials: C
authors.lastname: Funck-Brentano
authors.forename: P
authors.initials: P
authors.lastname: Jaillon
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D002110:Caffeine / Q000097:blood* / Q000493:pharmacokinetics; D000697:Central Nervous System Stimulants / Q000097:blood* / Q000493:pharmacokinetics; D019388:Cytochrome P-450 CYP1A2 / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D013806:Theophylline / Q000097:blood* / Q000493:pharmacokinetics; D013997:Time Factors
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine; D013806:Theophylline; D019388:Cytochrome P-450 CYP1A2; C021183:1,7-dimethylxanthine