Is Thioguanine safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Thioguanine. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
Thioguanine is an active metabolite of azathioprine. Numerous infants breastfed during maternal azathioprine in dosages up to 250 mg daily have been reported with no adverse effects noted. See the Azathioprine record for details. Ninety-nine women, mostly with Crohn s disease, who were taking thioguanine were followed during pregnancy and postpartum. In 98 pregnancies, thioguanine was continued during breastfeeding (extent not stated) in 38% of infants. No reported complications were reported in the 37 breastfed infants.[3]
Effects on milk supply
Relevant published information was not found as of the revision date.
Levels in milk
Maternal Levels. Four women receiving an immunomodulator to treat inflammatory bowel disease had metabolite levels measured in milk during the first 6 weeks postpartum. The abstract does not mention the specific drug and dose being taken, but the azathioprine metabolite 6-thioguanine nucleosides (6-TGNs) were measured. Although therapeutic levels were found in maternal serum, 6-TGNs was undetectable ( 123 mcg/L) in milk (time of collection not stated).[8] One woman received thioguanine for inflammatory bowel disease during pregnancy and lactation. She was receiving thioguanine 0.7 mg/kg daily in divided doses to treat colitis. Her breastmilk level at delivery was 48 nanomoles/L (8.03 mcg/L).[9] Infant Levels. Four infants were breastfed (3 exclusively, 1 rarely received formula) during maternal use of azathioprine orally in dosages of 1.2 to 2.1 mg/kg daily. All of the mothers and infants had the wild type TPMT *1/*1 genotype and all of the mothers had normal enzyme activity. At 3 to 3.5 months of age, all of the infants had undetectable blood levels of 6-TGNs.[10] Three infants whose mothers were taking azathioprine for inflammatory bowel disease (n = 2) or systemic lupus erythematosus (n = 1) were breastfed during maternal use of azathioprine. Azathioprine doses were 100 mg (plus prednisolone), 150 mg (plus infliximab) and 175 mg daily. In 1 infant, thioguanine was low, but detectable in blood at 3 days of age; at 3 weeks of age, thioguanine was not detectable. In another infant, thioguanine was undetectable at 3 weeks of age. Neither assay limits nor specific maternal doses were stated in the published abstract.[11] A woman began taking azathioprine 100 mg (1.4 mg/kg) daily for Crohn's disease while breastfeeding (extent not stated) her 3-month-old infant. After 8 days and 3 months of maternal therapy, 6-TGNs were measured, although breastfeeding had been tapered to zero by 3 months. On both occasions, 6-TGNs were not detectable in the blood of the infant. The as
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.