- During the first week, blood (about 1 teaspoon) will be drawn to check the status of the disease before each dose of the filgrastim and plerixafor combination and again 4 to 8 hours after receiving the study drugs. If participant's doctor feels it is needed, additional blood may be drawn after the 2nd blood draw to check the status of the disease. If participant's doctor feels it is needed, these blood draws may continue after the first week if the disease is not responding.