Can I take montelukast while pregnant or breastfeeding?
A plain-words look at what the NHS, the US drug label and LactMed say about montelukast.
In short
Pregnancy: Montelukast can be taken while you're pregnant.
Breastfeeding: Montelukast can be taken while breastfeeding, provided your doctor, health visitor or midwife is happy that your baby is healthy.
Your doctor, midwife or pharmacist can help you decide.
What this means for you
Pregnancy
- Keeping your asthma well controlled is important, as breathing difficulties in pregnancy can be dangerous for you and your baby.
- If you become pregnant while on montelukast, speak to your doctor.
- They may want to review your medicine to make sure you're on the best asthma treatment.
Breastfeeding
- Carrying on with montelukast is important to keep your symptoms under control, and breastfeeding also has benefits for both you and your baby.
- Information on montelukast in breastfeeding is limited, but it shows that tiny amounts reach breast milk.
- It has not been known to cause side effects in breastfed babies.
- If you have any worries, contact your health visitor, midwife, doctor or pharmacist promptly.
- This includes if your baby is not feeding as well as they usually do, seems unusually sleepy or irritable, or has diarrhoea.
Talk to your doctor or pharmacist
This page is educational, not advice for your own situation. Talk to your doctor, midwife or pharmacist before you start, stop or change any medicine in pregnancy or while breastfeeding.
The details: what each source says
Montelukast in pregnancy
The NHS says
Montelukast can be taken while you're pregnant. Keeping your asthma well controlled is important, as breathing difficulties in pregnancy can be dangerous for you and your baby.
If you become pregnant while on montelukast, speak to your doctor. They may want to review your medicine to make sure you're on the best asthma treatment.
In our words, from the NHS page Montelukast (nhs.uk). Contains public sector information licensed under the Open Government Licence v3.0 (OGL v3.0). The NHS does not endorse this site.
The US drug label says
8.1 Pregnancy Risk Summary Available data from published prospective and retrospective cohort studies over decades with montelukast use in pregnant women have not established a drug-associated risk of major birth defects [see Data] . In animal reproduction studies, no adverse developmental effects were observed with oral administration of montelukast to pregnant rats and rabbits during organogenesis at doses approximately 100 and 110 times, respectively, the maximum recommended human daily oral dose (MRHDOD) based on AUCs [see Data]. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
Prescribing label, section “8.1 Pregnancy” (opening excerpt): Montelukast Sodium (oral), Preferred Pharmaceuticals Inc. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Montelukast while breastfeeding
The NHS says
Montelukast can be taken while breastfeeding, provided your doctor, health visitor or midwife is happy that your baby is healthy.
Carrying on with montelukast is important to keep your symptoms under control, and breastfeeding also has benefits for both you and your baby.
Information on montelukast in breastfeeding is limited, but it shows that tiny amounts reach breast milk. It has not been known to cause side effects in breastfed babies.
If you have any worries, contact your health visitor, midwife, doctor or pharmacist promptly. This includes if your baby is not feeding as well as they usually do, seems unusually sleepy or irritable, or has diarrhoea.
In our words, from the NHS page Montelukast (nhs.uk). Contains public sector information licensed under the Open Government Licence v3.0 (OGL v3.0). The NHS does not endorse this site.
LactMed says
Very low levels of montelukast appear in breastmilk. Montelukast is approved for use in children as young as 6 months of age and has been used in neonates in dosages far greater than the amounts in breastmilk. Amounts ingested by the infant would not be expected to cause any adverse effects in breastfed infants. International guidelines consider that leukotriene receptor antagonists can be used during breastfeeding.[1,2]
“Summary of Use during Lactation”, LactMed record “Montelukast” (LM600), quoted verbatim. Everything LactMed reports about Montelukast while breastfeeding.
The US prescribing label says
8.2 Lactation Risk Summary A published clinical lactation study reports the presence of montelukast in human milk. Data available on the effects of the drug on infants, either directly [see Use in Specific Populations ( 8.4 )] or through breast milk, do not suggest a significant risk of adverse reactions from exposure to montelukast sodium. The effects of the drug on milk production are unknown. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for montelukast sodium and any potential adverse reactions on the breastfed infant from montelukast sodium or from the underlying maternal condition.
Prescribing label, section “8.2 Lactation”: Montelukast Sodium (oral), Preferred Pharmaceuticals Inc. Label on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Other names
UK brand names (per the NHS): Singulair.
Indian brands (per NPPA): Montair.
Indian combination brands that include montelukast: Montair LC.
Sources
- NHS, Montelukast (nhs.uk), page last reviewed 14 March 2023. Paraphrased. Contains public sector information licensed under the Open Government Licence v3.0.
- US drug label: Montelukast Sodium (oral), Preferred Pharmaceuticals Inc., human prescription drug, label effective 28 July 2026, set ID 64a3b181-e8d8-4caf-9f1b-e0063d0bd94a. DailyMed (National Library of Medicine). Public domain; quoted verbatim.
- Drugs and Lactation Database (LactMed), National Institute of Child Health and Human Development (NICHD), via NCBI Bookshelf, record “Montelukast” (LM600), bulk release of 22 September 2026. LactMed on NCBI Bookshelf. Public domain; quoted verbatim. LactMed is a registered trademark of the U.S. Department of Health and Human Services.
Sources checked 26 September 2026. How we source and check every page.
Educational summary of named sources, not medical advice.