title: Gender difference in letrozole pharmacokinetics in rats.
abstract: OBJECTIVE
  To study gender difference in letrozole (Letr) pharmacokinetics in rats.
  
  
  METHODS
  Letr concentrations in plasma and tissues were determined after ig administration of Letr 2 mg/kg. Recoveries of Letr in urine and feces were also analyzed.
  
  
  RESULTS
  Marked gender differences were found 6 h after ig Letr 2 mg/kg, the plasma concentrations of Letr in male rats were significantly (P < 0.01) lower than those in female rats. For example, at 24, 36, 48, and 72 h after administration, plasma concentrations in female rats were about 3.3, 5.6, 10.5, and 7.4-fold of that of male rats, respectively. AUC value of Letr in male was only about one-third of that in female rats. Estimated terminal phase half-lives (T1/2) were 10.5 and 40.4 h, respectively. In female rats, cumulative excreted fractions of Letr in urine and feces were 5.8% +/- 1.4% and 6.6% +/- 1.1% within 120 h after administration, respectively, but in male rats, the excreted fractions of Letr in urine and feces were only 1.30% +/- 0.59% and 0.87% +/- 0.31%. Letr concentrations in female rat tissues were significantly (P < 0.01) higher than those in male rat tissues 24 h after administration.
  
  
  CONCLUSIONS
  There are marked gender differences in Letr pharmacokinetics in rats.
authors.affiliation: Center of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China. xdliu@jlonline.com
authors.forename: X D
authors.initials: XD
authors.lastname: Liu
authors.forename: L
authors.initials: L
authors.lastname: Xie
authors.forename: Y
authors.initials: Y
authors.lastname: Zhong
authors.forename: C X
authors.initials: CX
authors.lastname: Li
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics; D001141:Aromatase / Q000493:pharmacokinetics; D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics*; D005260:Female; D000077289:Letrozole; D008297:Male; D009570:Nitriles / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D014018:Tissue Distribution; D014230:Triazoles / Q000493:pharmacokinetics*
chemical_list: D000970:Antineoplastic Agents; D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D009570:Nitriles; D014230:Triazoles; D000077289:Letrozole; D001141:Aromatase