Last update Dec. 7, 2022


Very Low Risk

Safe. Compatible. Minimal risk for breastfeeding and infant.

Coumarin-type anticoagulant drug vitamin K antagonist used for the treatment and prophylaxis of thromboembolic disorders. It works by depressing the hepatic synthesis of vitamin K-dependent coagulation factors.Oral or intravenous administration. Initially it was used as a rodenticide.

Warfarin is detected in breast milk in null or clinically insignificant amounts. (McKenna 1983, Orme 1979 y 1977, De Swiet 1977)

Not problems have been observed in infants whose mothers were treated. (Ito 1993, McKenna 1983)

Plasma levels of warfarin in such infants were undetectable. (Ito 1993, McKenna 1983)

Even in cases of accidental maternal overdosing, infants did not show any clinical problem and/or coagulation tests were not altered. (Schindler 2011)

Several medical societies and experts authors consider the use of this medication to be safe or very probably safe during breastfeeding. (LactMed, Azenkot 2022, Sucker 2020, Bates 2018, 2012 & 1997, Schaefer 2015, Marshall 2014, Rowe 2013, Fuller 2013, Yurdakök 2012, Middeldorp 2011, Amir 2011, Dresang 2008, Clark 2000, Greer 1998, Letsky 1997, Leys 1997, Hirsh 1995, Olthof 1993, Ginsberg 1988)

American Academy of Pediatrics: medication usually compatible with breastfeeding (AAP 2001). Recommendations for Drugs in the Eleventh WHO Model List of Essential Drugs: compatible with Breastfeeding. (WHO 2002)


We do not have alternatives for (RS)-4-Hydroxy-3-(3-oxo-1-phenylbutyl)coumarin since it is relatively safe.

Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.

Jose Maria Paricio, Founder & President of APILAM/e-Lactancia

Your contribution is essential for this service to continue to exist. We need the generosity of people like you who believe in the benefits of breastfeeding.

Thank you for helping to protect and promote breastfeeding.

José María Paricio, founder of e-lactancia.

Other names

(RS)-4-Hydroxy-3-(3-oxo-1-phenylbutyl)coumarin is Warfarin in Chemical name.

Is written in other languages:

(RS)-4-Hydroxy-3-(3-oxo-1-phenylbutyl)coumarin is also known as


(RS)-4-Hydroxy-3-(3-oxo-1-phenylbutyl)coumarin belongs to these groups or families:


Main tradenames from several countries containing (RS)-4-Hydroxy-3-(3-oxo-1-phenylbutyl)coumarin in its composition:


Variable Value Unit
Oral Bioavail. 100 %
Molecular weight 308 daltons
Protein Binding 99 %
VD 0.14 l/Kg
pKa 5.56 -
Tmax 4 (1 - 9) hours
40 (21 - 60) hours
M/P ratio 0.2 -
Theoretical Dose <0.0001 mg/Kg/d
Relative Dose 0.01 %
Ped.Relat.Dose 0.003 %


  1. Azenkot T, Schwarz EB. Special Considerations for Women of Reproductive Age on Anticoagulation. J Gen Intern Med. 2022 Aug;37(11):2803-2810. Abstract Full text (link to original source)
  2. Sucker C. Prophylaxis and Therapy of Venous Thrombotic Events (VTE) in Pregnancy and the Postpartum Period. Geburtshilfe Frauenheilkd. 2020 Jan;80(1):48-59. Abstract Full text (link to original source)
  3. Bates SM, Rajasekhar A, Middeldorp S, McLintock C, Rodger MA, James AH, Vazquez SR, Greer IA, Riva JJ, Bhatt M, Schwab N, Barrett D, LaHaye A, Rochwerg B. American Society of Hematology 2018 guidelines for management of venous thromboembolism: venous thromboembolism in the context of pregnancy. Blood Adv. 2018 Nov 27;2(22):3317-3359. Abstract Full text (link to original source)
  4. Marshall AL. Diagnosis, treatment, and prevention of venous thromboembolism in pregnancy. Postgrad Med. 2014 Abstract
  5. Rowe H, Baker T, Hale TW. Maternal medication, drug use, and breastfeeding. Pediatr Clin North Am. 2013 Feb;60(1):275-94. Abstract
  6. Fuller KP, Turner G, Polavarapu S, Prabulos AM. Guidelines for use of anticoagulation in pregnancy. Clin Lab Med. 2013 Abstract
  7. Yurdakök M. Fetal and neonatal effects of anticoagulants used in pregnancy: a review. Turk J Pediatr. 2012 Abstract
  8. Bates SM, Greer IA, Middeldorp S, Veenstra DL, Prabulos AM, Vandvik PO; American College of Chest Physicians. VTE, thrombophilia, antithrombotic therapy, and pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012 Feb;141(2 Suppl):e691S-e736S. Abstract Full text (link to original source) Full text (in our servers)
  9. Middeldorp S. How I treat pregnancy-related venous thromboembolism. Blood. 2011 Abstract Full text (link to original source) Full text (in our servers)
  10. Schindler D, Graham TP. Warfarin Overdose in a Breast-feeding Woman. West J Emerg Med. 2011 Abstract Full text (link to original source)
  11. Amir LH, Pirotta MV, Raval M. Breastfeeding--evidence based guidelines for the use of medicines. Aust Fam Physician. 2011 Sep;40(9):684-90. Review. Abstract Full text (link to original source) Full text (in our servers)
  12. Dresang LT, Fontaine P, Leeman L, King VJ. Venous thromboembolism during pregnancy. Am Fam Physician. 2008 Abstract
  13. WHO / UNICEF. BREASTFEEDING AND MATERNAL MEDICATION Recommendations for Drugs in the Eleventh WHO Model List of Essential Drugs. Department of Child and Adolescent Health and Development (WHO/UNICEF) 2002 Abstract Full text (link to original source) Full text (in our servers)
  14. AAP - American Academy of Pediatrics Committee on Drugs. Transfer of drugs and other chemicals into human milk. Pediatrics. 2001 Sep;108(3):776-89. Abstract Full text (link to original source) Full text (in our servers)
  15. Clark SL, Porter TF, West FG. Coumarin derivatives and breast-feeding. Obstet Gynecol. 2000 Abstract
  16. Greer IA. The special case of venous thromboembolism in pregnancy. Haemostasis. 1998 Abstract
  17. Leys D, Lamy C, Lucas C, Hénon H, Pruvo JP, Codaccioni X, Mas JL. Arterial ischemic strokes associated with pregnancy and puerperium. Acta Neurol Belg. 1997 Abstract
  18. Letsky EA. Peripartum prophylaxis of thrombo-embolism. Baillieres Clin Obstet Gynaecol. 1997 Abstract
  19. Bates SM, Ginsberg JS. Anticoagulants in pregnancy: fetal effects. Baillieres Clin Obstet Gynaecol. 1997 Abstract
  20. Hirsh J. Optimal intensity and monitoring warfarin. Am J Cardiol. 1995 Abstract
  21. Ito S, Blajchman A, Stephenson M, Eliopoulos C, Koren G. Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medication. Am J Obstet Gynecol. 1993 May;168(5):1393-9. Abstract
  22. Olthof E, de Vries TW. [Breast feeding and oral anticoagulants]. Tijdschr Kindergeneeskd. 1993 Abstract
  23. Ginsberg JS, Hirsh J. Optimum use of anticoagulants in pregnancy. Drugs. 1988 Abstract
  24. McKenna R, Cole ER, Vasan U. Is warfarin sodium contraindicated in the lactating mother? J Pediatr. 1983 Abstract
  25. Orme ML, Serlin MJ, Breckenridge A. Thromboembolism in pregnancy. Br Med J. 1979 Abstract Full text (link to original source)
  26. Orme ML, Lewis PJ, de Swiet M, Serlin MJ, Sibeon R, Baty JD, Breckenridge AM. May mothers given warfarin breast-feed their infants? Br Med J. 1977 Abstract Full text (link to original source)
  27. De Swiet M, Lewis PJ. Excretion of anticoagulants in human milk. N Engl J Med. 1977 Abstract

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