Can I take mesalazine while pregnant or breastfeeding?
A plain-words look at what the NHS, the US drug label and LactMed say about mesalazine.
In short
Pregnancy: If you already take mesalazine, you can keep taking it in pregnancy.
Breastfeeding: If your baby is healthy, you can usually take or use mesalazine while breastfeeding, but speak to your doctor first.
Your doctor, midwife or pharmacist can help you decide.
What this means for you
Pregnancy
- Keeping your inflammatory bowel disease (IBD) well controlled is important.
- There is no evidence that mesalazine taken in pregnancy harms your baby.
- Talk to your doctor if you become pregnant while on mesalazine.
- Do not stop your medicine unless your doctor says so.
- Your doctor can talk you through the risks and benefits of mesalazine and help you pick the most suitable treatment for you and your baby.
Breastfeeding
- Mesalazine reaches breast milk in small amounts, which should not give your baby side effects.
- Many people have used it while breastfeeding with no problems, although there have been a few rare cases of diarrhoea in babies.
- Side effects in breastfed babies from medicines their mother takes are very rare, but it's important to keep an eye on your baby whenever you take a medicine while breastfeeding.
- Keep taking the medicine and carry on breastfeeding as normal until you've had advice about your baby's symptoms.
When to get help
- Contact a healthcare professional or call 111 (NHS 111 in the UK) as soon as you can if your baby is feeding less well than normal, has diarrhoea, is vomiting (being sick), has a rash, or is irritable.
- For symptoms not mentioned here, or if you're worried about your baby, you can also speak to any healthcare professional or call 111.
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
Mesalazine in pregnancy
The NHS says
If you already take mesalazine, you can keep taking it in pregnancy. Keeping your inflammatory bowel disease (IBD) well controlled is important. There is no evidence that mesalazine taken in pregnancy harms your baby.
Talk to your doctor if you become pregnant while on mesalazine. Do not stop your medicine unless your doctor says so.
Your doctor can talk you through the risks and benefits of mesalazine and help you pick the most suitable treatment for you and your baby.
In our words, from the NHS page Mesalazine (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 Published data from meta-analyses, cohort studies and case series on the use of mesalamine during pregnancy have not reliably informed an association with mesalamine and major birth defects, miscarriage, or adverse maternal or fetal outcomes (see Data). In animal reproduction studies, there were no adverse developmental outcomes with administration of oral mesalamine during organogenesis to pregnant rats and rabbits at doses 1.7 and 5.4 times, respectively, the maximum recommended human dose (see Data). The estimated background risk of major birth defects and miscarriage for the indicated populations is unknown. Adverse outcomes in pregnancy occur regardless of the health of the mother or the use of medications. 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): MESALAMINE (oral), Camber Pharmaceuticals, Inc. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Mesalazine while breastfeeding
The NHS says
If your baby is healthy, you can usually take or use mesalazine while breastfeeding, but speak to your doctor first.
Mesalazine reaches breast milk in small amounts, which should not give your baby side effects. Many people have used it while breastfeeding with no problems, although there have been a few rare cases of diarrhoea in babies.
Side effects in breastfed babies from medicines their mother takes are very rare, but it's important to keep an eye on your baby whenever you take a medicine while breastfeeding.
Contact a healthcare professional or call 111 (NHS 111 in the UK) as soon as you can if your baby is feeding less well than normal, has diarrhoea, is vomiting (being sick), has a rash, or is irritable.
For symptoms not mentioned here, or if you're worried about your baby, you can also speak to any healthcare professional or call 111.
Keep taking the medicine and carry on breastfeeding as normal until you've had advice about your baby's symptoms.
In our words, from the NHS page Mesalazine (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
Mesalamine is poorly excreted into breastmilk. However, rather high levels of the mesalamine metabolite N-acetyl-5-ASA appear in breastmilk and its effects on breastfed infants are unknown. A few cases of diarrhea have been reported in infants exposed to mesalamine, although the rate is not high. Most experts consider mesalamine derivatives to be safe during breastfeeding.[1-7] If mesalamine is required by the mother, it is not a reason to discontinue breastfeeding, but carefully observe breastfed infants for diarrhea during maternal use of mesalamine.
“Summary of Use during Lactation”, LactMed record “Mesalamine” (LM443), quoted verbatim. Everything LactMed reports about Mesalamine while breastfeeding.
What these words mean
- metabolite
- a substance made when the body breaks down a medicine
Definitions adapted from the NCI Dictionary of Cancer Terms (National Cancer Institute).
The US prescribing label says
8.2 Lactation Risk Summary Data from published literature report the presence of mesalamine and its metabolite, N-acetyl 5-aminosalicylic acid in human milk in small amounts with relative infant doses (RID) of 2% or less (see Data) . There are case reports of diarrhea in breastfed infants exposed to mesalamine (see Clinical Considerations). There is no information on the effects of the drug on milk production. The lack of clinical data during lactation precludes a clear determination of the risk of mesalamine extended-release capsules to an infant during lactation; therefore, the developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for mesalamine extended-release capsules and any potential adverse effects on the breastfed child from mesalamine extended-release capsules or from the underlying maternal condition.
Prescribing label, section “8.2 Lactation” (opening excerpt): MESALAMINE (oral), Camber Pharmaceuticals, Inc. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.
Other names
UK brand names (per the NHS): Asacol, Mezavant, Octasa, Pentasa, Salofalk, Zintasa.
US name: mesalamine.
Sources
- NHS, Mesalazine (nhs.uk), page last reviewed 6 March 2025. Paraphrased. Contains public sector information licensed under the Open Government Licence v3.0.
- US drug label: MESALAMINE (oral), Camber Pharmaceuticals, Inc., human prescription drug, label effective 10 December 2025, set ID ef471372-8d9f-4d95-9371-44522c69058f. 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 “Mesalamine” (LM443), 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.