What Is Zarxio?

Zarxio (Filgrastim-sndz) is an injectable prescription medication that helps your body make more white blood cells called neutrophils. It belongs to a class of drugs known as granulocyte colony-stimulating factors (G-CSFs). Zarxio is a biosimilar to Neupogen (Filgrastim), meaning it is a near-identical copy of the original biologic drug made by Amgen. Zarxio is manufactured by Sandoz, a division of Novartis.

In fact, Zarxio was the first biosimilar approved in the United States when the FDA cleared it in 2015. It works the same way as Neupogen but is available at a lower cost, making it an important treatment option for patients who need G-CSF therapy.

Brand Name, Generic Name, and Drug Class

Understanding the different names for this medication can help you communicate with your doctors and pharmacists:

• Brand name: Zarxio
• Generic name: Filgrastim-sndz (the "-sndz" suffix identifies it as a biosimilar made by Sandoz)
• Reference product: Neupogen (Filgrastim) by Amgen
• Drug class: Colony-stimulating factor (CSF) / Granulocyte colony-stimulating factor (G-CSF)
• Other names you might hear: Filgrastim, G-CSF

Zarxio is not a controlled substance and does not have abuse potential.

What Is Zarxio Used For?

Zarxio is FDA-approved for several important uses, all related to boosting neutrophil (white blood cell) production:

1. Preventing infections during chemotherapy

This is the most common use. Chemotherapy kills cancer cells, but it also damages healthy bone marrow cells that make white blood cells. When your neutrophil count drops too low — a condition called neutropenia — you become very vulnerable to infections. Zarxio helps prevent this dangerous drop, a complication known as febrile neutropenia.

2. Recovery after bone marrow transplant

After receiving high-dose chemotherapy followed by a bone marrow transplant, Zarxio helps speed up the recovery of your white blood cells, reducing the time you spend at high risk for infection.

3. Severe chronic neutropenia

Some people have ongoing low neutrophil counts due to congenital (born with it), cyclic (comes and goes), or idiopathic (unknown cause) neutropenia. Zarxio can help maintain safer neutrophil levels in these patients over the long term.

4. Stem cell mobilization

Before certain types of stem cell transplants, Zarxio is used to move stem cells from the bone marrow into the bloodstream where they can be collected through a process called leukapheresis.

How Is Zarxio Taken?

Zarxio is given as an injection — either under the skin (subcutaneous) or through an IV (intravenous). It is not available as a pill or liquid to take by mouth.

Dosage forms

Zarxio comes in:

• Prefilled syringes: 300 mcg/0.5 mL and 480 mcg/0.8 mL
• Single-dose vials: 300 mcg/1 mL and 480 mcg/1.6 mL

Typical dosing

The standard dose is 5 to 10 mcg/kg per day, adjusted based on your specific condition and how your body responds. Your doctor will determine the right dose for you based on your weight and blood test results.

How to give yourself the injection

Many patients learn to give themselves Zarxio injections at home using the prefilled syringe. Here are the basics:

1. Remove the syringe from the refrigerator and let it sit at room temperature for about 30 minutes
2. Do not shake the syringe
3. Choose an injection site — your abdomen, outer thigh, or upper arm
4. Clean the area with an alcohol swab
5. Pinch the skin and insert the needle at a 45- to 90-degree angle
6. Inject the medication slowly
7. Dispose of the used syringe in a sharps container

Your nurse or pharmacist will give you detailed training before you start self-injecting. If you are not comfortable giving yourself shots, a family member or caregiver can be trained to help.

Timing with chemotherapy

For chemotherapy patients, Zarxio is usually started 24 hours after your last chemotherapy dose. It should not be given within 24 hours before or after chemo, because rapidly dividing bone marrow cells could be damaged by the chemotherapy drugs. Treatment continues daily until your neutrophil count recovers to a safe level.

Who Should Not Take Zarxio?

Zarxio is not right for everyone. You should not take Zarxio if you:

• Have had a serious allergic reaction to Filgrastim, Pegfilgrastim (Neulasta), or any ingredient in Zarxio
• Have a known allergy to proteins made from E. coli bacteria (Filgrastim is produced using E. coli)

Tell your doctor before starting Zarxio if you:

• Have sickle cell disease or sickle cell trait — Zarxio can trigger serious sickle cell crises
• Are pregnant or planning to become pregnant — Zarxio is Pregnancy Category C
• Are breastfeeding — it is not known whether Zarxio passes into breast milk
• Have any kidney problems
• Are taking Lithium, which can increase neutrophil production when combined with Zarxio

For a full list of medications to be aware of, read our guide on Zarxio drug interactions.

How Much Does Zarxio Cost?

Zarxio is a specialty medication, and the cost can be significant:

• Without insurance: $250 to $450 per prefilled syringe (480 mcg)
• Full course of treatment: A typical chemotherapy cycle may require multiple daily injections, totaling $2,500 to $6,000 or more per cycle
• Compared to Neupogen: Neupogen costs $500 to $900 per syringe, so Zarxio offers meaningful savings as a biosimilar

Insurance coverage

Most commercial insurance plans and Medicare Part B cover Zarxio, often as a preferred biosimilar over the more expensive Neupogen. However, prior authorization is commonly required, and many plans require dispensing through a specialty pharmacy.

Ways to save

There are several programs that can help reduce your out-of-pocket costs:

• Sandoz One Source — Copay assistance for commercially insured patients
• Novartis Patient Assistance Foundation — Free medication for eligible uninsured or underinsured patients
• NeedyMeds and RxAssist — Databases of patient assistance programs

For a complete breakdown of savings options, check out our guide to saving money on Zarxio.

Key Things to Remember About Zarxio

• Zarxio is a biosimilar to Neupogen that boosts white blood cell production
• It is used for chemotherapy-related neutropenia, bone marrow transplant recovery, severe chronic neutropenia, and stem cell mobilization
• It is given as a daily injection, usually starting 24 hours after chemotherapy
• Common side effects include bone pain, headache, and injection site reactions
• It must be refrigerated and should not be shaken or frozen
• Zarxio has been experiencing intermittent shortages, so plan ahead when filling your prescription

Need to find Zarxio in stock? Search Medfinder to check pharmacy availability near you.