Pharmacokinetics of Granulocyte Colony Stimulating Factor in the Breast Milk of Volunteer Peripheral Blood Stem Cell Donor

Study Summary

Background: \- The drug filgrastim (rGCSF) increases the number of blood-forming cells in the bloodstream. These cells can be collected from donors bloodstreams and used for transplant. Studies have shown that rGCSF is present in the breast milk of nursing mothers who are taking it. Based on these studies, it is now recommended that a nursing mother should not breastfeed from the time she receives the first dose of the drug until 2 days after the final dose. Researchers want to study the amount of the drug and its effect on the cells present in donor blood and breast milk. They hope to better understand the effects of this drug on breast milk. Objectives: \- To understand the effects of filgrastim on breast milk. Eligibility: \- Women enrolled in NIH protocol 00-CC-0165 and currently breastfeeding. Design: * Participants will receive rGCSF daily for 5 days. They will have blood taken daily. * Participants will get a freezer bag containing 10 sterile, labeled containers for breast milk collection. * Participants will transfer some of the breast milk they pump into one of the containers. They will write the date and time the milk was collected on the container. They will freeze the samples. Any remaining milk should be disposed of. * Participants will bring the samples to NIH on the day of their stem cell collection procedure. * For days 1 and 2 after stem cell collection, participants will continue to collect and freeze breast milk samples and dispose of any remaining milk. * For days 3 5 after stem cell collection, participants will collect and freeze samples. They can also resume normal breastfeeding. * A research nurse will arrange to collect the samples.