When You Can't Find Zarxio, There Are Other Options

If you've been prescribed Zarxio (filgrastim-sndz) and your pharmacy can't fill it, you're probably feeling anxious. This medication plays an important role in protecting your immune system during cancer treatment, and delays can put your health at risk.

But here's the reassuring news: Zarxio is not the only medication that does what it does. There are several alternatives in the same drug class that your doctor can prescribe instead. In this guide, we'll explain what Zarxio does, how it works, and walk through four alternatives that may be available when Zarxio is not.

What Is Zarxio and What Does It Do?

Zarxio is a biosimilar version of Neupogen (filgrastim), made by Sandoz. It was the first biosimilar approved in the United States in 2015. A biosimilar is essentially a near-identical copy of an existing biologic drug — it works the same way and produces the same clinical results.

Zarxio is prescribed to help your body make more neutrophils, a type of white blood cell that fights bacterial infections. When chemotherapy kills cancer cells, it also kills many of your healthy immune cells, leaving you vulnerable to serious infections. This condition is called neutropenia, and when it leads to fever, it's called febrile neutropenia — a medical emergency.

Zarxio helps prevent this by boosting your neutrophil production. For a deeper look, read our guide on what Zarxio is, its uses, and dosage.

How Does Zarxio Work?

Zarxio contains filgrastim-sndz, a man-made version of a protein your body produces naturally called granulocyte colony-stimulating factor (G-CSF). This protein signals your bone marrow to ramp up production of neutrophils and release them into your bloodstream.

Under normal conditions, your body makes G-CSF as needed. But after chemotherapy, your bone marrow is suppressed and can't keep up. Zarxio essentially gives your bone marrow the extra push it needs to recover faster. For a more detailed explanation, see our article on how Zarxio works.

4 Alternatives to Zarxio

All of the alternatives below work through the same basic mechanism — stimulating your bone marrow to produce more white blood cells. The main differences are in how they're manufactured, how often you need injections, and cost. Your doctor will choose the best option based on your specific treatment plan, insurance coverage, and what's available.

1. Neupogen (Filgrastim)

Neupogen is the original brand-name filgrastim, made by Amgen. Zarxio was specifically designed to be a biosimilar to Neupogen, so the two medications are nearly identical in how they work and how they're given.

• How it's given: Subcutaneous injection (under the skin) or intravenous infusion, typically once daily
• Typical treatment: Daily injections starting 24 hours after chemotherapy until neutrophil counts recover
• Key difference from Zarxio: Same medication, but brand-name pricing — Neupogen typically costs $500 to $900 per syringe, compared to $250 to $450 for Zarxio
• Good option if: Zarxio is unavailable and your insurance covers Neupogen

2. Granix (Tbo-filgrastim)

Granix is another short-acting G-CSF medication made by Teva Pharmaceuticals. While it's not technically a biosimilar to Neupogen (it was approved through a different regulatory pathway), it works the same way — stimulating neutrophil production.

• How it's given: Subcutaneous injection, once daily
• Typical treatment: Daily injections starting 24 hours after chemotherapy
• Key difference from Zarxio: Different manufacturing process, but similar efficacy and safety profile
• Good option if: Both Zarxio and Neupogen are unavailable

3. Neulasta (Pegfilgrastim)

Neulasta is a long-acting form of filgrastim made by Amgen. The "peg" in pegfilgrastim refers to a polyethylene glycol molecule attached to filgrastim, which allows it to stay in your body longer. Instead of daily injections, you need just one injection per chemotherapy cycle.

• How it's given: Single subcutaneous injection per chemo cycle, or via the Neulasta Onpro on-body injector (delivers the dose automatically about 27 hours after application)
• Typical treatment: One injection per chemotherapy cycle
• Key difference from Zarxio: Fewer injections (one vs. multiple daily), but higher cost per injection — typically $5,000 to $8,000 per dose
• Good option if: You prefer fewer injections and your insurance covers it

4. Udenyca (Pegfilgrastim-cbqv)

Udenyca is a biosimilar to Neulasta, made by Coherus BioSciences. It offers the same long-acting, one-injection-per-cycle convenience as Neulasta, often at a lower cost.

• How it's given: Single subcutaneous injection per chemotherapy cycle
• Typical treatment: One injection per chemo cycle
• Key difference from Zarxio: Long-acting (one shot instead of daily shots), biosimilar pricing may be lower than brand Neulasta
• Good option if: Your doctor recommends a long-acting G-CSF and you want a lower-cost alternative to Neulasta

How to Talk to Your Doctor About Switching

If you can't find Zarxio, the most important step is to contact your oncologist's office right away. Don't wait. Explain that you've been unable to fill your prescription and ask about alternatives.

Here are some helpful questions to ask:

• "Which alternative G-CSF would you recommend for my treatment plan?"
• "Will switching medications affect my treatment in any way?"
• "Can your office help me with prior authorization for the alternative?"
• "Is there a specialty pharmacy you recommend that might have Zarxio in stock?"

Your doctor may also want to adjust your dosing schedule if you switch from a short-acting product (like Zarxio) to a long-acting one (like Neulasta or Udenyca), or vice versa.

Check Availability Before Switching

Before you and your doctor decide on an alternative, it's worth checking whether that alternative is actually available too. G-CSF shortages sometimes affect multiple products at once.

Use Medfinder to check real-time pharmacy stock for Zarxio and its alternatives. You can search by drug name and zip code to see what's in stock near you.

Final Thoughts

Not being able to find Zarxio is stressful, but it doesn't mean you're out of options. Neupogen, Granix, Neulasta, and Udenyca all serve the same purpose — protecting your immune system when it's most vulnerable. Your oncologist can help you choose the right alternative and navigate any insurance hurdles that come with switching.

The most important thing is to act quickly. Don't wait days hoping your pharmacy will get Zarxio back in stock. Call your doctor, explore alternatives, and use tools like Medfinder to find what's available near you. Your health depends on getting this medication on time.

For more information about the current supply situation, read our Zarxio shortage update for 2026. And if cost is a concern, check out our guide on how to save money on Zarxio.