Allopurinol Pregnancy and Breastfeeding Warnings
Allopurinol Pregnancy Warnings
Allopurinol has been assigned to pregnancy category C by the FDA. Animal studies using high doses have revealed evidence of fetotoxicity and teratogenicity; it is not clear if these effects are a result of direct toxicity or maternal toxicity. There are no controlled data in human pregnancy. Allopurinol should only be given during pregnancy when benefit outweighs risk.
Allopurinol Breastfeeding Warnings
Allopurinol and its active metabolite, oxypurinol, are excreted into human milk. The effects in the nursing infant are unknown. The manufacturer recommends that caution be used when administering allopurinol to nursing women. Allopurinol is considered compatible with breast-feeding by the American Academy of Pediatrics.
In a case study of a 5-week old infant, the excretion of allopurinol and oxypurinol into human milk was evaluated following maternal ingestion of allopurinol 300 mg once daily for 4 weeks. Milk allopurinol levels were 0.9 and 1.4 mcg/mL, with corresponding milk to plasma ratios of 0.9 and 1.4, at 2 and 4 hours post-dose, respectively. Milk oxypurinol levels were 53.7 and 48 mcg/mL, with corresponding milk to plasma ratios of 3.9 and 2.4, at 2 and 4 hours post-dose, respectively. Two hours after breast-feeding (4 hours post-dose), allopurinol levels were undetectable in the infant's serum while oxypurinol was present at a concentration of 6.6 mcg/mL. There was no evidence of side effects in the infant, including no changes in standard clinical chemistry and hematology, during 6 weeks of maternal allopurinol therapy and regular breast-feeding (150 mL/kg/day).
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