Mifepristone

Drug Levels and Effects:




Summary of Use during Lactation:


Limited information indicates that breastfeeding need not be interrupted after a single dose of mifepristone. A dose of 200 mg might be preferable to a 600 mg dose in nursing mothers


Drug Levels:


Maternal Levels.

Twelve women (most 6 to 12 months postpartum) who had undergone a medical abortion using mifepristone andmisoprostolprovided milk samples for up to 5 days after the procedure for measurement of mifepristone. In the 2 women who received a single dose of 200 mg orally, mifepristone was undetectable (<5.6 mcg/L) in breastmilk at all times. Among the 10 women who received a single oral dose of 600 mg, average mifepristone breastmilk levels were 172 mcg/L on day 1 (n = 9) ; 66 mcg/L on day 2 (n = 9); 31 mcg/L on day 3 (n = 10); 24 mcg/L on day 4 (n = 4); and, 25 mcg/L on day 5 (n = 3). Breastmilk levels of mifepristone were highest in the samples collected between 6 and 9 hours after drug administration. Samples collected between 9 and 15 hours after the dose had much lower mifepristone levels. The authors estimated that a fully breastfed infant would receive a weight-adjusted dosage of 0.5% of the maternal dosage. They suggested that breastfeeding need not be interrupted after a single dose of mifepristone and that a dose of 200 mg might be preferable to a 600 mg dose in nursing mothers.[1]

Infant Levels.

Relevant published information was not found as of the revision date.


Effects in Breastfed Infants:


Relevant published information was not found as of the revision date.


Possible Effects on Lactation:


Based on animal data, some authors suggest that mifepristone used at term might shorten the onset of lactation, increase milk flow and increase the initial growth rate of breastfed infants.[2][3][4] However, no human data are available.


References:


1. Saav I, Fiala C, Hamalainen JM et al. Medical abortion in lactating women - low levels of mifepristone in breast milk. Acta Obstet Gynecol Scand. 2010. PMID:20367522
2. Baird DT. Antigestogens. Br Med Bull. 1993;49:73-87. PMID:8324617
3. Permezel M. The antiprogesterone steroid, RU 486 (mifepristone). Aust N Z J Obstet Gynaecol. 1990;30:77-80. PMID:2189395
4. Ulmann A, Dubois C. Anti-progesterones in obstetrics, ectopic pregnancies and gynaecological malignancy. Baillieres Clin Obstet Gynaecol. 1988;2:631-8. PMID:3069266



Substance Identification:




Substance Name:

Mifepristone

CAS Registry Number:

84371-65-3

Drug Class:


  • Contraceptives, Oral, Synthetic

  • Contraceptives, Postcoital, Synthetic

  • Hormone Antagonists

  • Luteolytic Agents

  • Menstruation-Inducing Agents

  • Abortifacient Agents, Steroidal


  • Administrative Information:




    LactMed Record Number:


    816


    Last Revision Date:


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