Last update April 25, 2022


Likely Compatibility

Fairly safe. Mild or unlikely adverse effects. Compatible under certain circumstances. Follow-up recommended. Read Commentary.

Cimetidine is a histamine H2 antagonist that inhibits gastric acid secretion and pepsin production. It is used in peptic ulcer disease and gastroesophageal reflux. Oral or parenteral administration one to four times daily.

It is excreted in breast milk in moderate amount (Oo 1995, Somogyi 1979), though lower than the dose used in newborns and infants (5 - 10 mg/kg/day). (Rowe 2013)

Several medical societies, experts and expert consensus, consider the use of this medication to be safe or very probably safe during breastfeeding. (Hale 2019, Briggs 2017, Rowe 2013, Mahadevan 2006, Richter 2005, Nice 2000, Lee 1993)

American Academy of Pediatrics: Maternal Medication Usually Compatible With Breastfeeding.

Until more published data is known about this drug in relation to breastfeeding, known safer alternatives are preferable (Rowe 2013, WHO 2002, Nice 2000. Lee 1992), especially during the neonatal period and in the event of prematurity.

Famotidine and Nizatidine are excreted into milk but in less proportion than Cimetidine or Ranitidine, which have been proposed as alternative to during lactation. (Schaefer 2015, Rowe 2013, Nice 2000, Hagemann 1998, Lee 1993)


  • Famotidine (Safe substance and/or breastfeeding is the best option.)
  • Nizatidine (Safe substance and/or breastfeeding is the best option.)
  • Omeprazole (Safe substance and/or breastfeeding is the best option.)

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

C10H16N6S is Cimetidine in Molecular formula.

Is written in other languages:

C10H16N6S is also known as


Main tradenames from several countries containing C10H16N6S in its composition:


Variable Value Unit
Oral Bioavail. 60 - 70 %
Molecular weight 252 daltons
Protein Binding 22 %
VD 1 l/Kg
pKa 13.38 -
Tmax 1.5 hours
2 hours
M/P ratio 12 -
Theoretical Dose 0.75 - 1.4 mg/Kg/d
Relative Dose 5 - 11.3 %
Ped.Relat.Dose 3.8 - 28 %


  1. Hale TW. Medications & Mothers' Milk. 1991- . Springer Publishing Company. Available from Consulted on April 10, 2024 Full text (link to original source)
  2. Briggs GG, Freeman RK, Towers CV, Forinash AB. Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk. Wolters Kluwer Health. Tenth edition (acces on line) 2015
  3. Rowe H, Baker T, Hale TW. Maternal medication, drug use, and breastfeeding. Pediatr Clin North Am. 2013 Feb;60(1):275-94. Abstract
  4. Mahadevan U, Kane S. American gastroenterological association institute technical review on the use of gastrointestinal medications in pregnancy. Gastroenterology. 2006 Jul;131(1):283-311. Review. Abstract Full text (link to original source) Full text (in our servers)
  5. Richter JE. Review article: the management of heartburn in pregnancy. Aliment Pharmacol Ther. 2005 Nov 1;22(9):749-57. Review. Abstract Full text (in our servers)
  6. 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)
  7. 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)
  8. Nice FJ, Snyder JL, Kotansky BC. Breastfeeding and over-the-counter medications. J Hum Lact. 2000 Nov;16(4):319-31. Review. Erratum in: J Hum Lact 2001 Feb;17(1):90. Abstract
  9. Hagemann TM. Gastrointestinal medications and breastfeeding. J Hum Lact. 1998 Sep;14(3):259-62. Review. Abstract
  10. Oo CY, Kuhn RJ, Desai N, McNamara PJ. Active transport of cimetidine into human milk. Clin Pharmacol Ther. 1995 Nov;58(5):548-55. Abstract
  11. Lee JJ, Rubin AP. Breast feeding and anaesthesia. Anaesthesia. 1993 Jul;48(7):616-25. Review. Abstract Full text (link to original source) Full text (in our servers)
  12. Somogyi A, Gugler R. Cimetidine excretion into breast milk. Br J Clin Pharmacol. 1979 Jun;7(6):627-9. No abstract available. Abstract Full text (link to original source)
  13. Carlson HE, Ippoliti AF. Cimetidine, an H2-antihistamine, stimulates prolactin secretion in man. J Clin Endocrinol Metab. 1977 Abstract

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