Can you take cladribine while breastfeeding?
What LactMed says
The National Library of Medicine’s own summary, quoted in full. We do not write a verdict of our own on this question, and we do not compress theirs into a label.
The amount of cladribine in milk is low with oral doses of 10 to 20 mg daily used in multiple sclerosis. Data in one patient indicates that the drug is rapidly eliminated over 24 hours and undetectable at 48 hours after a dose. Manufacturers recommend a 7-day (Europe) or 10-day (US) breastfeeding abstinence period after a dose. Chemotherapy may adversely affect the normal microbiome and chemical makeup of breastmilk. Women who receive chemotherapy during pregnancy are more likely to have difficulty nursing their infant.
Quoted from Cladribine — Drugs and Lactation Database (LactMed®), National Institute of Child Health and Human Development, revised June 15, 2025.
What LactMed would consider instead
LactMed ends this record by naming the drugs it would consider in place of cladribine. Whether any of them fits depends on what you are treating — this is the database’s list, not a recommendation from us.
- Glatiramer
- Immune Globulin
- Interferon beta
- Methylprednisolone
- Natalizumab
- Ocrelizumab
- Ofatumumab
- Peginterferon beta
How much cladribine gets into breastmilk
Maternal Levels. A woman with multiple sclerosis who was 4 months postpartum began cladribine. In her second course of therapy, 5 weeks after the first course, she received 20 mg cladribine once daily by mouth on days 1 to 3 and 10 mg on days 4 and 5. On day 3, the patient collected samples at 0, 1, 2, 4, 6, 8, 12, and 24 hours after a 20 mg dose. The highest milk level was 281 mcg/L at 1 hour after the dose. Levels declined rapidly over 12 to 24 hours, to undetectable (<1.5 mcg/L) levels at 48 hours and beyond. The average milk level was 44 mcg/L over the 24 hour period. The authors calculated that a fully breastfed infant would receive a dose of 6.6 mcg/kg daily, which corresponds to a weight-adjusted dose of 3.1% of the maternal dose. A further analysis of two patients taking cladribine for multiple sclerosis found relative infant dosages of 2.99% with a 10 mg daily dosage and 4.73% with a 20 mg daily dosage. Peak milk concentrations were seen at 1 and 2 hours after the dose, respectively.
Infant Levels. Relevant published information was not found as of the revision date.
What has been seen in breastfed infants
Relevant published information was not found as of the revision date.
Effects on milk supply
Relevant published information was not found as of the revision date.
Frequently asked questions
Can you take cladribine while breastfeeding?
The amount of cladribine in milk is low with oral doses of 10 to 20 mg daily used in multiple sclerosis. The full record is quoted on this page, and the decision is one to make with the person who prescribed it — LactMed itself states it is not a substitute for professional judgement.
What can I take instead of cladribine while breastfeeding?
LactMed lists Glatiramer, Immune Globulin, Interferon beta, Methylprednisolone, Natalizumab, Ocrelizumab, Ofatumumab, Peginterferon beta as alternate drugs to consider. That is the database's own list for this drug — whether any of them suits you depends on what you are treating.
Does cladribine pass into breastmilk?
LactMed's measured drug levels for cladribine are quoted in full on this page, under "How much gets into breastmilk".
Do I need to pump and dump after taking cladribine?
LactMed does not frame its records that way — it reports measured drug levels in milk and what has been observed in breastfed infants, which is what this page quotes. "Pump and dump" advice for a specific drug and dose should come from your clinician or a pharmacist, not from a general rule.
More on cladribine
LactMed states that the information it presents is not a substitute for professional judgement, and that you should consult your healthcare provider for breastfeeding advice related to your particular situation. Nothing on this page is medical advice.