The Basics
What is Mercaptopurine?
Used alone or with other chemotherapy drugs to treat acute lymphocytic leukemia.
Brand names for Mercaptopurine
Purinethol
How Mercaptopurine is classified
Antineoplastic Agents, Antimetabolites, Immunosuppressive Agents
Mercaptopurine During Pregnancy
Mercaptopurine pregnancy category
Category DNote that the FDA has deprecated the use of pregnancy categories, so for some medications, this information isn’t available. We still think it’s useful to list historical info, however, given what a common proxy this has been in the past.
What we know about taking Mercaptopurine while pregnant
Mercaptopurine can cause fetal harm when administered to a pregnant woman. Women receivingmercaptopurine in the first trimester of pregnancy have an increased incidence of abortion; therisk of malformation in offspring surviving first trimester exposure is not accurately known. In aseries of 28 women receiving mercaptopurine after the first trimester of pregnancy, 3 mothersdied undelivered, 1 delivered a stillborn child, and 1 aborted; there were no cases ofmacroscopically abnormal fetuses. Since such experience cannot exclude the possibility of fetaldamage, mercaptopurine should be used during pregnancy only if the benefit clearly justifies thepossible risk to the fetus, and particular caution should be given to the use of mercaptopurine inthe first trimester of pregnancy.There are no adequate and well-controlled studies in pregnant women. If this drug is used duringpregnancy or if the patient becomes pregnant while taking the drug, the patient should be apprisedof the potential hazard to the fetus. Women of childbearing potential should be advised to avoidbecoming pregnant.
Taking Mercaptopurine While Breastfeeding
What are recommendations for lactation if you're taking Mercaptopurine?
Most sources consider breastfeeding to be contraindicated during maternal antineoplastic drug therapy, although antimetabolites such as mercaptopurine appear to pose the least risk to breastfed infants.[1] After high-dose chemotherapy, it might be possible to breastfeed safely during intermittent therapy with an appropriate period of breastfeeding abstinence. Although no data are available to determine an appropriate period to withhold breastfeeding, the drug’s terminal half-life suggests that withholding breastfeeding for 1 to 2 days may be sufficient. Chemotherapy may adversely affect the normal microbiome and chemical makeup of breastmilk.[2] In the treatment of conditions such as ulcerative colitis and Crohn’s disease, low doses of mercaptopurine (6-MP) for immunosuppression appear to be acceptable.[3][4][5][6][7][8] No active metabolites of mercaptopurine were found in the blood of breastfed infants whose mothers were taking azathioprine and no adverse effects attributable to mercaptopurine or azathioprine have been noted. See the Azathioprine record for details. Mothers with decreased activity of the enzyme that detoxifies mercaptopurine metabolites may transmit higher levels of drug to their infants in breastmilk. It might be desirable to monitor exclusively breastfed infants with a complete blood count with differential, and liver function tests if mercaptopurine is used during lactation, although some authors feel that monitoring is unnecessary.[9] Avoiding breastfeeding for 4 hours after a dose should markedly decrease the dose received by the infant in breastmilk.[10]
Maternal / infant drug levels
Most sources consider breastfeeding to be contraindicated during maternal antineoplastic drug therapy, although antimetabolites such as mercaptopurine appear to pose the least risk to breastfed infants.[1] After high-dose chemotherapy, it might be possible to breastfeed safely during intermittent therapy with an appropriate period of breastfeeding abstinence. Although no data are available to determine an appropriate period to withhold breastfeeding, the drug’s terminal half-life suggests that withholding breastfeeding for 1 to 2 days may be sufficient. Chemotherapy may adversely affect the normal microbiome and chemical makeup of breastmilk.[2] In the treatment of conditions such as ulcerative colitis and Crohn’s disease, low doses of mercaptopurine (6-MP) for immunosuppression appear to be acceptable.[3][4][5][6][7][8] No active metabolites of mercaptopurine were found in the blood of breastfed infants whose mothers were taking azathioprine and no adverse effects attributable to mercaptopurine or azathioprine have been noted. See the Azathioprine record for details. Mothers with decreased activity of the enzyme that detoxifies mercaptopurine metabolites may transmit higher levels of drug to their infants in breastmilk. It might be desirable to monitor exclusively breastfed infants with a complete blood count with differential, and liver function tests if mercaptopurine is used during lactation, although some authors feel that monitoring is unnecessary.[9] Avoiding breastfeeding for 4 hours after a dose should markedly decrease the dose received by the infant in breastmilk.[10]
Possible effects of Mercaptopurine on milk supply
Relevant published information was not found as of the revision date.
Possible alternatives to Mercaptopurine
(Immunosuppression) Cyclosporine, Tacrolimus; (Inflammatory Bowel Disease) Budesonide, Infliximab, Mesalamine, Prednisone; (Systemic Lupus Erythematosus) Hydroxychloroquine, Prednisone.
List of References
Lactation sources: Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK501922/1. Pistilli B, Bellettini G, Giovannetti E et al. Chemotherapy, targeted agents, antiemetics and growth-factors in human milk: How should we counsel cancer patients about breastfeeding? Cancer Treat Rev. 2013;39:207-11. PMID: 23199900
2. Urbaniak C, McMillan A, Angelini M et al. Effect of chemotherapy on the microbiota and metabolome of human milk, a case report. Microbiome. 2014;2:24. PMID: 25061513
3. Ha C, Dassopoulos T. Thiopurine therapy in inflammatory bowel disease. Expert Rev Gastroenterol Hepatol. 2010;4:575-88. PMID: 20932143
4. Van Assche G, Dignass A, Reinisch W et al. The second European evidence-based Consensus on the diagnosis and management of Crohn’s disease: Special situations. J Crohns Colitis. 2010;4:63-101. PMID: 21122490
5. Nielsen OH, Maxwell C, Hendel J. IBD medications during pregnancy and lactation. Nat Rev Gastroenterol Hepatol. 2014;11:116-27. PMID: 23897285
6. Nguyen GC, Seow CH, Maxwell C et al. The Toronto Consensus Statements for the Management of IBD in Pregnancy. Gastroenterology. 2016;150:734-57. PMID: 26688268
7. van der Woude CJ, Ardizzone S, Bengtson MB et al. The second European evidenced-based consensus on reproduction and pregnancy in inflammatory bowel disease. J Crohns Colitis. 2015;9:107-24. PMID: 25602023
8. Mahadevan U, Robinson C, Bernasko N et al. Inflammatory bowel disease in pregnancy clinical care pathway: A report from the American Gastroenterological Association IBD Parenthood Project Working Group. Gastroenterology. 2019;156:1508-24. PMID: 30658060
9. Christensen LA, Dahlerup JF, Nielsen MJ et al. Azathioprine treatment during lactation: authors’ reply. Aliment Pharmacol Ther. 2009;30:91. PMID: 19566905
10. Bar-Gil Shitrit A, Grisaru-Granovsky S, Ben Ya’acov A et al. Management of inflammatory bowel disease during pregnancy. Dig Dis Sci. 2016;61:2194-204. PMID: 27068171
11. Coulam CB, Moyer TP, Jiang NS et al. Breast-feeding after renal transplantation. Transplant Proc. 1982;13:605-9. PMID: 6817481
12. Kane SV, Present DH. Metabolites to immunomodulators are not detected in breast milk. Am J Gastroenterol. 2004;99 (10 Suppl S):S246-7 Abstract 761. DOI: doi:10.1111/j.1572-0241.2004.001_1.x
13. Gardiner SJ, Gearry RB, Roberts RL, Zhang M, Barclay ML, Begg EJ. Exposure to thiopurine drugs through breast milk is low based on metabolite concentrations in mother-infant pairs. Br J Clin Pharmacol. 2006;62:453-6. PMID: 16995866
14. de Meij TG, Jharap B, Kneepkens CM et al. Long-term follow-up of children exposed intrauterine to maternal thiopurine therapy during pregnancy in females with inflammatory bowel disease. Aliment Pharmacol Ther. 2013;38:38-43. PMID: 23675854
15. Mahadevan U, Martin CF, Sandler RS et al. PIANO: a 1000 patient prospective registry of pregnancy outcomes in women with IBD exposed to immunomodulators and biologic therapy. Gastroenterology. 2012;142 (5 Suppl 1):S149. Abstract 865.
16. Beswick L, Shukla D, Friedman AB et al. National audit: Assessing the use and safety of allopurinol thiopurine co-therapy in pregnant females with inflammatory bowel disease. J Gastroenterol Hepatol. 2016;31 (Suppl 2):128-9. Abstract. DOI: doi:10.1111/jgh.13521
Disclaimer: This material is provided for educational purposes only and is not intended for medical advice, diagnosis, or treatment. Consult your healthcare provider with any questions.
