Can you take allopurinol 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.
Limited information indicates that a maternal dose of allopurinol of 300 mg daily provides near-therapeutic dose and plasma levels in an exclusively breastfed infant. The manufacturer recommends avoiding allopurinol during breastfeeding and for one week after the last dose. If the mother requires allopurinol, it is not a reason to discontinue breastfeeding, but exclusively breastfed infants should be monitored if this drug is used, including observation for allergic reactions (such as rash) and periodic CBC and differential blood counts.
Quoted from Allopurinol — Drugs and Lactation Database (LactMed®), National Institute of Child Health and Human Development, revised March 15, 2025.
What LactMed would consider instead
LactMed ends this record by naming the drugs it would consider in place of allopurinol. Whether any of them fits depends on what you are treating — this is the database’s list, not a recommendation from us.
How much allopurinol gets into breastmilk
Allopurinol is metabolized to oxypurinol which has xanthine oxidase inhibitory activity equal to allopurinol's. Oxypurinol is absorbed well from the gastrointestinal tract.
Maternal Levels. A woman who was 5 weeks postpartum had been taking allopurinol 300 mg orally for 4 weeks. Two hours after a dose her breastmilk contained 0.9 mg/L of allopurinol and 53.7 mg/L of its active metabolite oxypurinol. Four hours after the dose, her breastmilk contained 1.4 mg/L of allopurinol and 48 mg/L of oxypurinol. The authors calculated that the exclusively breastfed infant would receive between 0.14 and 0.2 mg/kg of allopurinol and between 7.2 to 8 mg/kg of oxypurinol daily. This dose of oxypurinol is slightly less than the infant allopurinol dose of 10 mg/kg daily.
Infant Levels. A 5-week-old infant whose mother had been taking allopurinol 300 mg daily for 4 weeks had plasma levels of allopurinol that was undetectable (<0.5 mg/L) and of oxypurinol that was 6.6 mg/L 2 hours after nursing and 4 hours after the mother's dose of allopurinol. This plasma level was 33 to 48% of the measured maternal plasma oxypurinol levels.
What has been seen in breastfed infants
One infant breastfed from age 1 week to age 7 weeks during maternal allopurinol therapy with 300 mg or allopurinol daily. The infant had no observable side effects and no changes in clinical chemistry and hematology values.
A national survey of gastroenterologists in Australia identified 21 infants who were breastfed by mothers taking a combination of allopurinol and a thiopurine (e.g. azathioprine, mercaptopurine) to treat inflammatory bowel disease. All had taken the combination during pregnancy also. Two postpartum infant deaths occurred, both at 3 months of age. One was a twin (premature birth-related) and the other from SIDS. The authors did not believe the deaths were medication related. No information was provided on the extent of breastfeeding, specific thiopurines, drug dosages or the outcomes of the other infants.
A single-center, retrospective study found 44 women with inflammatory bowel disease who had 62 pregnancies and 59 live births who took low-dose azathioprine in combination with allopurinol during pregnancy and postpartum. Eighty-four percent of their infants were breastfed and no serious signals or complications were reported first year of life.
Effects on milk supply
Relevant published information was not found as of the revision date.
Frequently asked questions
Can you take allopurinol while breastfeeding?
What the NIH's Drugs and Lactation Database says about Allopurinol while breastfeeding — quoted in full. 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 allopurinol while breastfeeding?
LactMed lists Probenecid 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 allopurinol pass into breastmilk?
LactMed's measured drug levels for allopurinol are quoted in full on this page, under "How much gets into breastmilk".
Do I need to pump and dump after taking allopurinol?
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 allopurinol
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.