Medications
Filgrastim-sndz (Zarxio)
A biosimilar copy of filgrastim (G-CSF): a daily injection under the skin or into a vein that helps the body make more infection-fighting white blood cells, used during chemotherapy and after bone-marrow transplant.
How Medicare covers it
Split path: Zarxio given in a clinic follows Part B (Q5101 — see the Part B basis in this package); self-injected at home it is listed in Part D formularies, and the Part D aggregation in this package is carried exactly as computed. Part A during a covered inpatient stay.
| Coverage details | |
|---|---|
| Part B status | CMS Part B Spending by Drug HCPCS file (RY26, data through 2024) carries Q5101 (filgrastim-sndz, Zarxio): the clinician-administered path is Part B. The file's J1442 row is originator filgrastim (Neupogen), a different product, explicitly NOT matched to this biosimilar package. |
| Medicare Advantage | Most Medicare Advantage plans that include drug coverage (MAPD plans) use the same formulary-and-tier system; the plan's own drug list decides coverage and copay — check the plan's formulary. |
| Medicare Supplement (Medigap) | Medicare Supplement (Medigap) plans sold today do not include prescription drug coverage; drug coverage comes from Part D or an MAPD plan. |
What it treats
Zarxio lowers the chance of infection from low white blood cells in people receiving strong chemotherapy, helps white cells recover after leukemia chemotherapy or bone marrow transplant, helps collect blood stem cells, treats severe chronic neutropenia, and increases survival in people exposed to high doses of radiation that damage bone marrow. Zarxio is a biosimilar to Neupogen (filgrastim).
What it is for, in depth
Filgrastim-sndz, sold as Zarxio, helps the body make more infection-fighting white blood cells. It lowers the chance of infection from low white blood cells in people receiving strong chemotherapy, helps white cells recover after leukemia chemotherapy or a bone marrow transplant, and helps collect blood stem cells. It also treats severe chronic neutropenia, a long-term low white cell condition, and increases survival in people exposed to high doses of radiation that damage bone marrow. Zarxio is a biosimilar to Neupogen. It comes as an injection in single-dose vials and prefilled syringes, given under the skin or into a vein, usually once or twice a day as the care team directs.
How it works
It is a leukocyte growth factor (G-CSF) that tells the bone marrow to make more neutrophils, a type of white blood cell that fights infection.
How it is taken
It is given as an injection under the skin or as an infusion into a vein, usually once or twice a day depending on the condition, following the care team's timing around chemotherapy or transplant. It comes in single-dose vials and prefilled syringes.
Common side effects
Common side effects depend on the condition and include fever, pain, rash, cough, and shortness of breath in people receiving chemotherapy. Nosebleed and rash are also listed for people with acute myeloid leukemia.
Serious warnings
Serious risks include a ruptured spleen (which can be fatal), acute respiratory distress syndrome (ARDS), severe allergic reactions including anaphylaxis, fatal sickle cell crises, and kidney inflammation (glomerulonephritis). Bone marrow problems (MDS/AML), low platelets, and inflammation of the aorta (aortitis) are also warned about on the label.
Who should be careful
People with a history of serious allergic reactions to filgrastim or pegfilgrastim products must not use Zarxio. People with sickle cell disorders, kidney problems, or breast or lung cancer receiving chemotherapy or radiation should be careful and monitored for the label's warnings, and anyone with left upper belly or shoulder pain should be checked for an enlarged or ruptured spleen.
Major interactions
The Zarxio label does not highlight a specific major drug interaction list; tell your care team about all medicines, especially chemotherapy and other bone-marrow treatments, so timing and blood counts can be managed.
Why it is in its tier
Filgrastim-sndz, sold as Zarxio, is listed by 78.11% of Part D plans, and its most common placement is Tier 5, used by 97.69% of listing plans. Tier 5 is the specialty tier, with the highest percentage coinsurance, so a person usually pays a percentage of the cost rather than a small flat copay. That placement fits what the data shows: Zarxio is a brand-name biosimilar injection, not a plain generic tablet, and it is used around chemotherapy and transplant care. In the CMS dashboard, average spending per beneficiary was $5178.58, which is a CMS program average, not a copay. Individual plans vary, so readers should check their own plan.
Sources
- ZARXIO (FILGRASTIM-SNDZ) INJECTION, SOLUTION [SANDOZ INC.] — DailyMed
- MedlinePlus — National Library of Medicine
- MedlinePlus — Filgrastim Injection
What official patient guides say
Scope note: MedlinePlus has no separate page for filgrastim-sndz — its Filgrastim Injection page says filgrastim injection refers to any of the biosimilar filgrastim products, and it lists Zarxio (filgrastim-sndz) among its brand names, so the daily-life facts below are that page's facts for filgrastim injection, including Zarxio. Filgrastim injection comes as a solution (liquid) in vials and prefilled syringes, injected under the skin or slowly or continuously into a vein, 1 to 2 times a day depending on the condition being treated. A nurse or other healthcare provider may give it, or you may be shown how to inject it under the skin at home. Use it exactly as directed, do not shake the vial or syringe, check that the solution has no particles and is not foamy, cloudy, or discolored and that the expiration date has not passed, and use each vial or syringe only once, disposing of used needles, syringes, and vials in a puncture-resistant container. The page gives no take-it-or-skip-it rule for a missed dose: if you inject it at home, talk to your doctor about what to do if you forget to inject it on schedule. Store it in the refrigerator in its container, tightly closed and out of reach of children; filgrastim (including Zarxio) may be kept at room temperature for up to 24 hours away from direct sunlight, and if you accidentally freeze it you may thaw it in the refrigerator, but dispose of a vial or syringe that is frozen a second time. Dispose of unneeded medication through a medicine take-back program; do not flush it.
Part D formulary coverage
| Formulary summary | |
|---|---|
| Most common tier | 5 |
| Plans listing this drug | 4292 |
| Total Part D plans | 5495 |
| Share of plans listing it | 78.11 |
| Formularies listing it | 169 |
| Tier | Plans |
|---|---|
| Tier 1 | 50 plans |
| Tier 4 | 49 plans |
| Tier 5 | 4193 plans |
Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.
What you pay
| With Medicare Part D | |
|---|---|
| Most common tier | Tier 5 |
| Typical copay | $0 — half of plans charge between $0 and $0 |
| Typical coinsurance | 26.0% of the price |
| Based on | 4113 plans that cover this drug · 2027 plan year |
A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.
Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-08
Similar medications
Other medications in the same FDA pharmacologic class (Leukocyte Growth Factor):
Read next
Part D spending averages (2024)
| Brand name | Generic name | Total claims 2024 | Total spending 2024 | Total beneficiaries 2024 | Rank by beneficiaries 2024 |
|---|---|---|---|---|---|
| Zarxio | Filgrastim-Sndz | 24638 | 4.82955e+07 | 9326 | 1018 |
Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30
Companies covering this drug
4,292 plans from 327 companies list this drug on a formulary for 2027. Search by company or plan name, or filter by tier. Cost sharing is the plan's published amount for this drug's tier in the initial coverage stage (1-month retail supply), where the plan publishes it; a blank means the plan does not publish it.
| Company | Plan | Tier | Copay | Coinsurance |
|---|
A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.
Coverage and costs change. Drug lists (formularies), tiers, and copays can change during the year and differ by plan. Always check with your insurance company or plan directly to confirm what is covered and what you will pay.
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