title: Repeated topical administration of all-trans-retinoic acid and plasma levels of retinoic acids in humans.
abstract: BACKGROUND
  Vitamin A ingestion raises plasma levels of several potentially teratogenic retinoic acids (RAs) with all-trans and 13-cis configuration, but definitive data concerning the consequences of topical administration of all-trans-RA are lacking.
  
  
  OBJECTIVE
  The study objective was to investigate the potential for inducing systemic activity after topical administration of 0.025% all-trans-RA by measuring plasma retinoid levels.
  
  
  METHODS
  Plasma levels of all-trans-RA, 13-cis-RA, and 4-oxo-13-cis-RA were measured in four healthy subjects before, during, and after 14 daily topical applications of all-trans-RA.
  
  
  RESULTS
  Topical administration of all-trans-RA did not significantly increase plasma levels of all-trans-RA, 13-cis-RA, and 4-oxo-13-cis-RA. Significant decreases in levels of these RAs observed during the night may reflect diurnal variations of retinoid metabolism or lowered absorption of dietary vitamin A.
  
  
  CONCLUSIONS
  Diurnal and nutritional factors influence plasma levels of endogenous retinoids to a greater extent than topical administration of all-trans-RA at doses used for acne therapy, which on the basis of these results appears unlikely to induce systemic effects.
authors.affiliation: CIRD Galderma, Valbonne, France.
authors.forename: P
authors.initials: P
authors.lastname: Buchan
authors.forename: C
authors.initials: C
authors.lastname: Eckhoff
authors.forename: D
authors.initials: D
authors.lastname: Caron
authors.forename: H
authors.initials: H
authors.lastname: Nau
authors.forename: B
authors.initials: B
authors.lastname: Shroot
authors.forename: H
authors.initials: H
authors.lastname: Schaefer
mesh_terms: D000287:Administration, Topical; D000328:Adult; D006801:Humans; D008297:Male; D014212:Tretinoin / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000493:pharmacokinetics*
chemical_list: D014212:Tretinoin