Milk-only Lactation Study for Patients on Eltrombopag

This is a Phase IV study to evaluate eltrombopag concentrations in breast milk of nursing mothers taking marketed eltrombopag (PROMACTA®). Up to 10 subjects (mother-infant pairs) at as many as 10 study centers in the US will be enrolled. Nursing mothers who are registered with the PROMACTA Pregnancy Registry will be offered the option to participate in this trial if they continue to take commercial eltrombopag post-delivery and decide to breastfeed their infant. Information will be collected in a diary. Breast milk samples will be collected before and after infant feedings for a 24 hour period after eltrombopag dosing to evaluate the eltrombopag concentrations in the breast milk. Mothers will also be given the option to have a pharmacokinetic (PK) blood sample collected from the infant.