Absolute bioavailability of letrozole in healthy postmenopausal women

Biopharm Drug Dispos. 1997 Dec;18(9):779-89. doi: 10.1002/(sici)1099-081x(199712)18:9<779::aid-bdd64>3.0.co;2-5.


Letrozole is a new non-steroidal inhibitor of the aromatase enzyme system. It is currently under development for the treatment of postmenopausal women with advanced breast cancer. Absolute bioavailability of letrozole when given orally as one 2.5 mg film-coated tablet in comparison to the same dose given intravenously as a bolus injection was studied in 12 healthy postmenopausal women. Letrozole absolute systemic bioavailability after p.o. administration was 99.9 +/- 16.3%. Elimination of letrozole was slow. Total-body clearance of letrozole from plasma after i.v. administration was low (2.21 L h-1). The calculated distribution volume at steady state (1.87 L kg-1) suggests a rather high tissue distribution. Biotransformation of letrozole is the main elimination mechanism with the glucuronide conjugate of the secondary alcohol metabolite being the predominant species found in urine. The two study treatments were tolerated equally well.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Area Under Curve
  • Aromatase Inhibitors*
  • Biological Availability
  • Biotransformation
  • Chromatography, High Pressure Liquid
  • Enzyme Inhibitors / administration & dosage
  • Enzyme Inhibitors / blood
  • Enzyme Inhibitors / pharmacokinetics*
  • Female
  • Humans
  • Injections, Intravenous
  • Letrozole
  • Middle Aged
  • Nitriles / administration & dosage
  • Nitriles / blood
  • Nitriles / pharmacokinetics*
  • Postmenopause / blood*
  • Regression Analysis
  • Tissue Distribution
  • Triazoles / administration & dosage
  • Triazoles / blood
  • Triazoles / pharmacokinetics*


  • Aromatase Inhibitors
  • Enzyme Inhibitors
  • Nitriles
  • Triazoles
  • Letrozole