No information is available on the clinical use of fostamatinib during breastfeeding. Because the active metabolite of fostamatinib (R406) is 98.3% bound to plasma proteins, the amount in milk is likely to be low. However, the active metabolites has a half-life of 15 hours, and might accumulate in the infant. The manufacturer recommends that breastfeeding be discontinued during fostamatinib therapy and for at least 1 month after the final dose.