title: Levonorgestrel pharmacokinetics in plasma and milk of lactating women who take 1.5 mg for emergency contraception.
abstract: BACKGROUND
  Progestin-only methods are among the contraceptive options available for breastfeeding women, however the doses of progestin used in emergency contraception (EC) have not been evaluated in nursing mothers. We therefore investigated the pharmacokinetics of 1.5 mg levonorgestrel (LNG) in lactating women.
  
  
  METHODS
  Twelve healthy exclusively breastfeeding volunteers received 1.5 mg LNG. Women refrained from nursing for 72 h after dosing and fed their infants with milk frozen beforehand. Serial blood and milk samples were collected for 120 h and assayed for LNG and sex hormone binding globulin.
  
  
  RESULTS
  LNG concentrations peaked in plasma and in milk 1-4 h and 2-4 h after dosing, respectively. Concentrations in milk (M) paralleled those in plasma (P) but were consistently lower (mean M:P ratio 0.28). Estimated infant exposure to LNG is 1.6 microg on the day of dosing (1 microg in the first 8 h), 0.3 microg on the second day and 0.2 microg on the third day.
  
  
  CONCLUSIONS
  Nursing mothers may need EC. These results suggest that to limit infant exposure to the period of maximum LNG excretion in milk, mothers should discontinue nursing for at least 8 h, but not more than 24 h, after EC.
authors.affiliation: Laboratoire HRA Pharma, Paris 75003, France. e.gainer@hra-pharma.com
authors.forename: E
authors.initials: E
authors.lastname: Gainer
authors.forename: R
authors.initials: R
authors.lastname: Massai
authors.forename: S
authors.initials: S
authors.lastname: Lillo
authors.forename: V
authors.initials: V
authors.lastname: Reyes
authors.forename: M L
authors.initials: ML
authors.lastname: Forcelledo
authors.forename: R
authors.initials: R
authors.lastname: Caviedes
authors.forename: C
authors.initials: C
authors.lastname: Villarroel
authors.forename: J
authors.initials: J
authors.lastname: Bouyer
mesh_terms: D000293:Adolescent; D000328:Adult; D001942:Breast Feeding; D044363:Contraception, Postcoital; D003281:Contraceptives, Postcoital / Q000097:blood* / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007774:Lactation; D016912:Levonorgestrel / Q000097:blood* / Q000493:pharmacokinetics*; D008895:Milk, Human / Q000737:chemistry*; D012738:Sex Hormone-Binding Globulin / Q000032:analysis
chemical_list: D003281:Contraceptives, Postcoital; D012738:Sex Hormone-Binding Globulin; D016912:Levonorgestrel