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Allopurinol Pregnancy and Breastfeeding Warnings

Allopurinol is also known as: Aloprim, Lopurin, Zyloprim

Medically reviewed on December 15, 2017

Allopurinol Pregnancy Warnings

This drug is only recommended for use during pregnancy when there are no alternatives and the benefit outweighs the risk.

AU TGA pregnancy category: B2
US FDA pregnancy category: C

While this drug has been in wide use for many years without apparent ill consequence, women of reproductive age rarely require treatment with this drug. Fetal harm was not been observed in rats and rabbits at doses up to 20 times the usual human dose (5 mg/kg/day), but an increased number of external and skeletal malformations were observed in fetuses of pregnant mice who had received 50 or 100 mg/kg intraperitoneally on gestation days 10 or 13. There were also an increased number of dead fetuses in these dams given 100 mg/kg, but not those given 50 mg/kg. It cannot be determined whether this may have been a fetal effect or an effect secondary to maternal toxicity. There are no adequate and well controlled trials in pregnant women.

AU TGA pregnancy category B2: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals are inadequate or may be lacking, but available data show no evidence of an increased occurrence of fetal damage.

US FDA pregnancy category C: Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

See references

Allopurinol Breastfeeding Warnings

Caution is recommended

Excreted into human milk: Yes

Comments: The effects in the nursing infant are unknown.

Allopurinol and its active metabolite oxypurinol are excreted into human breast milk. Based on a case study in a 5-week old breastfed infant, the calculated daily dose of allopurinol and oxypurinol received by an exclusively breastfed infant would be between 0.14 and 0.2 mg/kg and 7.2 to 8 mg/kg, respectively. Limited data have found no observable side effects in breastfed infants. If this drug is needed, monitor breastfed infants closely for allergic reactions (e.g. rash), and perform periodic blood counts (including a differential).

See references

References for pregnancy information

  1. "Product Information. Aloprim (allopurinol)." Nabi, Boca Raton, FL.
  2. "Product Information. Zyloprim capsules (allopurinol)." Glaxo Wellcome, Research Triangle Park, NC.
  3. Cerner Multum, Inc. "Australian Product Information." O 0
  4. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

References for breastfeeding information

  1. "Product Information. Zyloprim capsules (allopurinol)." Glaxo Wellcome, Research Triangle Park, NC.
  2. United States National Library of Medicine "Toxnet. Toxicology Data Network. Available from: URL:" ([cited 2013 -]):
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  4. Cerner Multum, Inc. "Australian Product Information." O 0

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.