title: Effect of letrozole on uterine tonus and contractility: a randomized controlled trial.
abstract: BACKGROUND
  Letrozole inhibits estrogen production. It has been shown to increase efficacy in medical abortion when used with misoprostol. This study investigated if letrozole acts as an abortifacient due to a synergistic effect with misoprostol on uterine contractility.
  
  
  METHODS
  Sixteen healthy women requesting surgical abortion were randomized to receive either no pretreatment or treatment with letrozole 7.5 mg daily for 3 days prior to the abortion. All women received misoprostol 400 mcg vaginally 3.5 h prior to surgery. Intrauterine pressure was measured for 30 min before and 3.5 h after misoprostol was given using an intrauterine pressure catheter. Main outcome measure was uterine contractility analyzed by repeated-measures analysis of variance.
  
  
  RESULTS
  At baseline, uterine contractions were absent and tonus was low. No significant difference was seen between the two groups in tonus (p=.818) or in contractility (p=.423) after misoprostol administration.
  
  
  CONCLUSIONS
  Letrozole does not appear to act as an abortifacient through an effect on uterine contractility or increased sensitivity to misoprostol of the uterine myometrium.
authors.affiliation: Division of Obstetrics and Gynaecology, Department of Women's and Children's Health, Karolinska Institutet/Karolinska University Hospital, 171 77 Stockholm, Sweden. Helena.kopp-kallner@ds.se
authors.forename: Helena
authors.initials: H
authors.lastname: Kopp Kallner
authors.forename: Pak Chung
authors.initials: PC
authors.lastname: Ho
authors.forename: Kristina
authors.initials: K
authors.lastname: Gemzell-Danielsson
mesh_terms: D000020:Abortifacient Agents, Nonsteroidal / Q000008:administration & dosage; D000028:Abortion, Induced / Q000379:methods*; D000282:Administration, Intravaginal; D000284:Administration, Oral; D000328:Adult; D047072:Aromatase Inhibitors / Q000008:administration & dosage; D004357:Drug Synergism; D005260:Female; D006801:Humans; D000077289:Letrozole; D016595:Misoprostol / Q000008:administration & dosage; D009215:Myometrium / Q000187:drug effects; D009570:Nitriles / Q000008:administration & dosage; D010120:Oxytocics / Q000008:administration & dosage; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011300:Preoperative Care; D013997:Time Factors; D014230:Triazoles / Q000008:administration & dosage; D014590:Uterine Contraction / Q000187:drug effects*; D055815:Young Adult
chemical_list: D000020:Abortifacient Agents, Nonsteroidal; D047072:Aromatase Inhibitors; D009570:Nitriles; D010120:Oxytocics; D014230:Triazoles; D016595:Misoprostol; D000077289:Letrozole