The median serum elimination half-life (t1/ 2) of filgrastim after single subcutaneous doses ranged from 2.7 hours (1.0 MU/ kg, 10 µg/ kg) to 5.7 hours (0.25 MU/ kg, 2.5 µg/ kg) and was prolonged after 7 days of dosing to 8.5 - 14 hours, respectively.