title: Effect of high-dose vitamin C on hepatic cytochrome P450 3A4 activity.
abstract: OBJECTIVE
  To investigate the effect of high-dose vitamin C on cytochrome P450 (CYP) 3A4 activity, and to evaluate possible sex-specific effects on CYP3A4 activity.
  
  
  METHODS
  Single-center longitudinal study.
  
  
  METHODS
  Tertiary- and specialty-care teaching hospital.
  
  
  METHODS
  Fourteen healthy Caucasian adult volunteers (seven men, seven women).
  
  
  METHODS
  Subjects self-administered vitamin C 500 mg twice/day for 14 days.
  
  
  RESULTS
  Hepatic CYP3A4 activity was measured by using the erythromycin breath test on days 1 (baseline) and 15. Overall, no significant effect of vitamin C on CYP3A4 activity was observed. Sex and baseline results were significant predictors of changes in CYP3A4 activity. In men, mean activity increased by 21.9% (95% confidence interval -3.88-47.6%). The effect in women was not consistent.
  
  
  CONCLUSIONS
  Sex and baseline CYP3A4 activity appeared to influence the effect of vitamin C on CYP3A4 activity.
authors.affiliation: Ottawa Hospital and Ottawa Health Research Institute, the University of Ottawa, Ontario, Canada. rvheesw1@tibbe.jnj.com
authors.forename: Rolf P G
authors.initials: RP
authors.lastname: van Heeswijk
authors.forename: Curtis L
authors.initials: CL
authors.lastname: Cooper
authors.forename: Brian C
authors.initials: BC
authors.lastname: Foster
authors.forename: Bobby M
authors.initials: BM
authors.lastname: Chauhan
authors.forename: Farshad
authors.initials: F
authors.lastname: Shirazi
authors.forename: Isabelle
authors.initials: I
authors.lastname: Seguin
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Phillips
authors.forename: Ed
authors.initials: E
authors.lastname: Mills
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004790:Enzyme Induction; D005260:Female; D006801:Humans; D008099:Liver / Q000201:enzymology*; D008137:Longitudinal Studies; D008297:Male; D012737:Sex Factors
chemical_list: D000975:Antioxidants; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D001205:Ascorbic Acid