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Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006-.

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Drugs and Lactation Database (LactMed) [Internet].

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Last Revision: February 15, 2021.

Estimated reading time: 2 minutes

CASRN: 73590-58-6

image 135012070 in the ncbi pubchem database

Drug Levels and Effects

Summary of Use during Lactation

Limited information indicates that maternal omeprazole doses of 20 mg daily produce low levels in milk and would not be expected to cause any adverse effects in breastfed infants.

Drug Levels

Maternal Levels. A woman taking oral omeprazole 20 mg daily for gastroesophageal reflux had omeprazole measured in her milk 3 weeks postpartum. The milk omeprazole level was not detectable for 90 minutes after the dose and then reached a peak of 20 mcg/L at 3 hours after the dose.[1] Using the peak milk level in this patient, the maximum dose that an exclusively breastfed infant would receive in breastmilk would be 3 mcg/kg daily or about 0.9% of the maternal weight-adjusted dosage. For comparison, doses of 1 mg/kg daily have been used in neonates.

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

Effects in Breastfed Infants

One mother taking oral omeprazole 20 mg daily pumped and discarded her milk once each day 4 hours after her morning dose. She breastfed her infant the remainder of the day for 3 months before weaning. The infant remained well at 12 months of age.[1]

Effects on Lactation and Breastmilk

The Spanish pharmacovigilance system found 20 cases of gynecomastia reported in patients taking omeprazole during the time period of 1982 to 2006.[2] A retrospective claims database study in the United States found that users of proton pump inhibitors had an increased risk of gynecomastia.[3]

A 13-year-old girl was placed on omeprazole 20 mg twice daily by mouth for dyspepsia caused by mefenamic acid and a Helicobacter pylori infection. After 2 days of therapy, she developed bilateral galactorrhea and elevated serum prolactin. Three weeks after discontinuing omeprazole, galactorrhea and hyperprolactinemia resolved. Six weeks later, she was rechallenged with omeprazole and her serum prolactin rose from 27 to 70 mcg/L. Prolactin returned to normal 2 weeks after omeprazole discontinuation. Over the next 6 months, she was given domperidone on one occasion and lansoprazole on another. With both drugs, she developed galactorrhea and hyperprolactinemia which returned to normal after drug discontinuation.[4] The prolactin level in a mother with established lactation may not affect her ability to breastfeed.

A 26-year-old woman with a kidney transplant developed galactorrhea after her kidney function decreased. She was taking tacrolimus, prednisone, amlodipine, labetalol, lovastatin, nortriptyline and pyridoxine as well as omeprazole for heartburn. Her omeprazole dose had been increased from 20 mg twice a day to 40 mg twice a day 3 months prior. A week earlier, she had been given prescriptions for naratriptan for migraine and metoclopramide for nausea at an emergency department visit. Her symptoms persisted 4 weeks later and her serum prolactin was elevated. Metoclopramide was discontinued with no improvement change in serum prolactin. Omeprazole was discontinued and calcium carbonate started. Two weeks later, her serum prolactin had normalized. Two months later, her heartburn increased and omeprazole was restarted at 20 mg daily with no increase in serum prolactin.[5] The patient’s hyperprolactinemia and galactorrhea were probably caused by omeprazole.

Alternate Drugs to Consider

Antacids, Cimetidine, Famotidine, Pantoprazole, Sucralfate


Marshall JK, Thompson AB, Armstrong D. Omeprazole for refractory gastroesophageal reflux disease during pregnancy and lactation. Can J Gastroenterol. 1998;12:225–7. [PubMed: 9582548]
Carvajal A, Macias D, Gutierrez A, et al. Gynaecomastia associated with proton pump inhibitors: A case series from the Spanish Pharmacovigilance System. Drug Saf. 2007;30:527–31. [PubMed: 17536878]
He B, Carleton B, Etminan M. Risk of gynecomastia with users of proton pump inhibitors. Pharmacotherapy. 2019;39:614–8. [PubMed: 30865318]
Jabbar A, Khan R, Farrukh SN. Hyperprolactinaemia induced by proton pump inhibitor. J Pak Med Assoc. 2010;60:689–90. [PubMed: 20726208]
Prikis M, MacDougall J, Narasimhadevara N. Proton pump inhibitor-induced galactorrhea in a kidney transplant recipient: A friend or foe? Case Rep Transplant. 2020;2020:8108730. [PMC free article: PMC7254079] [PubMed: 32566351]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

Breast Feeding


Anti-Ulcer Agents

Gastrointestinal Agents

Proton Pump Inhibitors

Disclaimer: Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.


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