Filgrastim Dosing for Stem Cell Donor Mobilization
For this 22-year-old healthy stem cell donor weighing 73 kg, administer filgrastim 10 mcg/kg/day subcutaneously for 5 consecutive days, which equals 730 mcg daily (rounded to the nearest vial size per institutional protocol), with apheresis collection performed on day 6.
Dosing Calculation and Rationale
The standard mobilization regimen for healthy allogeneic donors uses 10 mcg/kg/day 1, 2:
- Daily dose: 73 kg × 10 mcg/kg = 730 mcg/day
- Duration: 5 days (days 1-5)
- Collection: Apheresis on day 6
- Route: Subcutaneous injection
This can be administered as either:
- Single daily dose of 10 mcg/kg, OR
- Split into two doses of 5 mcg/kg twice daily 3
Recent evidence shows no significant difference in CD34+ cell yield between once-daily versus twice-daily dosing schedules, though twice-daily may produce slightly higher peripheral CD34+ counts on day 5 3. The once-daily regimen offers greater convenience with equivalent efficacy.
Evidence Supporting This Dose
The FDA label specifically describes mobilization studies using 5 to 30 mcg/kg/day for PBPC collection, with the most common effective dose being 10 mcg/kg/day 1. Research demonstrates that:
- 10 mcg/kg/day for 5 days produces optimal CD34+ cell mobilization in healthy donors 2
- All donors receiving this regimen achieved adequate collection (>4 × 10⁶ CD34+ cells/kg recipient weight) in a single apheresis 2
- Lower doses (3-5 mcg/kg/day) may be insufficient, with overlapping confidence intervals but significantly lower peak CD34+ counts 2
- The dose of 8 mcg/kg/day showed adequate results but was less consistent than 10 mcg/kg/day 4
Timing of Collection
Peak mobilization occurs on days 4-6, with most donors showing maximal CD34+ cell counts on day 5 2, 4. Therefore:
- Administer filgrastim on days 1,2,3,4, and 5
- Perform apheresis on day 6 (after 5 full days of mobilization)
- Consider checking peripheral blood CD34+ count on day 5 to predict apheresis yield (r = 0.87 correlation) 2
Important Clinical Considerations
Vial rounding: The calculated dose of 730 mcg should be rounded to the nearest vial size according to your institutional weight-based limits 5. Filgrastim is commonly available in 300 mcg and 480 mcg vials, so this donor would receive either 720 mcg (300 + 300 + 120) or 780 mcg (300 + 480) depending on available vial sizes.
Monitoring: The donor should be monitored for common adverse effects including bone pain (30% incidence), headache, and fatigue 1. These are generally mild and well-tolerated in healthy donors.
Alternative option: While pegfilgrastim (a single 6 mg dose) has been studied for donor mobilization 6, it is not FDA-approved for this indication and the guidelines do not support its use in this context 5. Stick with daily filgrastim.
Recipient Context (AML)
The fact that the recipient has AML is relevant for the transplant team but does not change the donor's filgrastim dosing. The mobilization regimen remains standard at 10 mcg/kg/day for 5 days regardless of recipient diagnosis. The recipient's AML will be managed separately with appropriate conditioning regimens prior to transplant 7.