Neulasta is a prescription drug used to lower infection risk in people with certain cancers and to treat radiation sickness. Continue reading to learn about Neulasta’s potential side effects, which range from mild to serious.

Neulasta is specifically used to:

  • Reduce infection risk from febrile neutropenia (a low level of a certain type of white blood cell) in people with nonmyeloid cancers. These are cancers that don’t affect the bone marrow.
  • Treat hematopoietic subsyndrome, a type of radiation sickness.

Neulasta comes in two forms: prefilled, single-dose syringes and on-body injector (OBI) patches called Neulasta Onpro. The OBI patches aren’t used to treat radiation sickness.

The active drug in Neulasta is pegfilgrastim, which is a biologic. Biologics are made from parts of living organisms.

For more information about Neulasta, including details about its uses, see this in-depth article on the drug.

Some people may experience mild or serious side effects during their Neulasta treatment. Examples of Neulasta’s commonly reported side effects, which are mild, include the following:

* To learn more about this side effect, see “Side effects explained” below.

Examples of mild side effects that have been reported with Neulasta include:

* To learn more about this side effect, see “Side effects explained” below.

In most cases, these side effects should be temporary, and some may be easily managed, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. And do not stop using Neulasta unless your doctor recommends it.

Neulasta may cause mild side effects other than the ones listed above. To find out more, see Neulasta’s patient information.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Neulasta, visit MedWatch.

Serious side effects from Neulasta aren’t common, but they can occur in rare cases.

Serious side effects that have been reported with Neulasta include:

* To learn more about this side effect, see “Side effects explained” below.

If you develop serious side effects while using Neulasta, call your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Get answers to some frequently asked questions about Neulasta’s side effects.

How long do side effects from Neulasta last?

Most people who get side effects from Neulasta only have mild symptoms. These should go away on their own after a few days. Side effects of the Neulasta shot or patch usually aren’t long in duration.

Although very rare, Neulasta may cause a ruptured spleen. (The spleen is an organ in your belly.) For more information, see the “Side effects explained” section below.

Before you start treatment with Neulasta, talk with your doctor and pharmacist about potential side effects. This should include long-term and short-term side effects.

Can Neulasta cause a fever?

No, fever isn’t an expected side effect of Neulasta.

But fever can be a symptom of other side effects of Neulasta. This includes some serious side effects, such as:

* For more information about ARDS, see the “Side effects explained” section below.

Fever can also be a sign that you have an infection. So you should tell your doctor right away if you get a fever during Neulasta treatment. They can help determine the cause and the best way to treat it.

Are there any long-term side effects of Neulasta?

Although very rare, Neulasta may cause a ruptured spleen. (The spleen is an organ in your belly.) For more information, see the “Side effects explained” section below.

Other serious side effects, including leukocytosis and glomerulonephritis, can usually be treated and should go away when you stop using Neulasta. Leukocytosis is an increased level of white blood cells called leukocytes. Glomerulonephritis is a condition that affects your kidneys. For more information about glomerulonephritis, see the “Side effects explained” section below.

If you have questions about how long Neulasta side effects can last, talk with your doctor or pharmacist.

Will using Neulasta make me tired?

No, Neulasta isn’t expected to make you tired or cause fatigue (lack of energy).

But fatigue can be a symptom of capillary leak syndrome. This is a rare but serious side effect of Neulasta that involves tiny blood vessels leaking. In addition to fatigue, other symptoms of capillary leak syndrome include:

If you have symptoms of capillary leak syndrome, you should call 911 or go to an emergency room. Capillary leak syndrome can be deadly in rare cases.

Keep in mind that fatigue is a common side effect of many anticancer drugs, which you may use with Neulasta. And fatigue is a common symptom of radiation sickness, which Neulasta is used to treat.

If you have questions about Neulasta and fatigue, talk with your doctor or pharmacist.

Is headache a side effect of Neulasta?

No, headache isn’t a known side effect of Neulasta. In studies, this side effect wasn’t reported by people who took the drug.

If you’re having headaches during your Neulasta treatment, talk with your doctor. They can help determine what’s causing them and suggest ways to treat them.

Learn more about some of the side effects Neulasta may cause.

Bone pain

Bone pain is a common side effect of Neulasta, though the reason for this isn’t known. It also isn’t known how long this side effect from the drug can last.

What might help

If you develop bone pain while using Neulasta, contact your doctor. They may suggest you take a pain reliever, such as ibuprofen (Advil, Motrin) or naproxen (Aleve). Or they may recommend you stop using Neulasta.

Ruptured spleen

Although it’s very rare, people prescribed Neulasta may develop a ruptured spleen. (The spleen is an organ in your belly.) There have been reports of this side effect in people using Neulasta. But it’s unclear how often this side effect happened or if Neulasta was the cause.

Symptoms of a ruptured spleen include:

What might help

A ruptured spleen is a life threatening condition that needs immediate medical attention. If you’re using Neulasta and have pain in your left shoulder or upper-left belly, call 911 or go to an emergency room right away.

Acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a rare, serious side effect of Neulasta. With this condition, your lungs become filled with fluid. This keeps your lungs from being able to supply your body with enough oxygen.

There have been reports of this side effect in people using Neulasta. But it’s unclear how often this side effect has happened or if Neulasta was the cause.

Symptoms of ARDS include:

What might help

Although very rare, ARDS can be life threatening, so it needs immediate medical attention. If you’re using Neulasta and feel short of breath or are having trouble breathing, call 911 or go to an emergency room right away.

Glomerulonephritis

Glomerulonephritis causes swelling in the glomeruli, which are blood vessel clusters in your kidneys. These organs help filter waste products out of your blood and into your urine.

There have been reports of glomerulonephritis in people using Neulasta. But it’s unclear how often this side effect has happened or if Neulasta was the cause.

Symptoms of this side effect include:

What might help

If you think you have symptoms of glomerulonephritis while using Neulasta, call your doctor. Usually, reducing your dose can help treat this side effect. But if this doesn’t work, your doctor may recommend trying a different drug to treat your condition.

Allergic reaction

Like most drugs, Neulasta can cause an allergic reaction in some people.

Symptoms, which can be mild or serious, include:

  • rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest an over-the-counter antihistamine, such as Benadryl (diphenhydramine), or a topical product, such as hydrocortisone cream, to manage your symptoms.

If your doctor confirms you had a mild allergic reaction to Neulasta, they’ll decide if you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you had a serious allergic reaction to Neulasta, they may have you switch to a different treatment.

Keeping track of side effects

During your Neulasta treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of drug you received when you had the side effect
  • how soon after starting that dose you had the side effect
  • what your symptoms were from the side effect
  • how it affected your daily activities
  • what other medications you were also taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help your doctor learn more about how a drug affects you. And your doctor can use this information to adjust your treatment plan if needed.

Neulasta may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you use Neulasta. Factors to consider include those in the list below.

Allergy to acrylics or latex. If you’re allergic to acrylics, you should not use Neulasta Onpro. This is because the on-body injector has an acrylic adhesive. But if you have a latex allergy, you should not use Neulasta prefilled syringes. The needle cap contains a natural rubber made from latex. Be sure to tell your doctor if you have an allergy to acrylics or latex before you use Neulasta.

Certain cancers. If you have a myeloid cancer (a kind of cancer involving bone marrow), you should not receive Neulasta. This is because the drug may cause tumor growth in people with this kind of cancer. (A tumor is an abnormal growth of cells.) Instead, talk with your doctor about other treatment options for your condition.

Sickle cell disorders. Neulasta can cause a sickle cell crisis (pain from clogged blood vessels) in someone with a sickle cell disorder. (Sickle cell disorders affect hemoglobin, which your body needs to move oxygen.) This can be fatal. If you have a sickle cell disorder, talk with your doctor about other treatment options for your condition.

Allergic reaction. If you’ve had an allergic reaction to Neulasta or any of its ingredients, you should not use Neulasta. Ask your doctor what other medications are better options for you.

Alcohol use and Neulasta

There aren’t known interactions between drinking alcohol and using Neulasta.

But if you’re taking chemotherapy drugs with Neulasta, alcohol may make certain side effects of chemotherapy worse. Alcohol could also interfere with some chemotherapy drugs.

If you drink alcohol, talk with your doctor about whether it is safe to have with your chemotherapy regimen. (For people with certain cancers, Neulasta is given after a dose of chemotherapy.)

Pregnancy and breastfeeding while using Neulasta

Pregnancy. It isn’t known if it’s safe to receive Neulasta while pregnant. Animal studies didn’t show harm to the fetus or pregnant female, but these don’t always predict what will happen in people.

If you’re pregnant or planning to become pregnant, talk with your doctor before using Neulasta. They can explain the risks and benefits of the drug as well as other treatment options.

Breastfeeding. It isn’t known if it’s safe to receive Neulasta while breastfeeding. It’s not known if the drug shows up in human breast milk. If you’re breastfeeding, talk with your doctor before using Neulasta. They can explain the risks and benefits of the drug as well as other treatment options.

Side effects from Neulasta aren’t common, and they’re usually mild when they do occur. Mild side effects of Neulasta are bone pain and pain in your arms or legs. Serious side effects from Neulasta can occur in rare cases.

If you have questions about Neulasta’s side effects, talk with your doctor or pharmacist. Ask questions to get the answers you need to feel confident about your treatment. Here are a few to get you started:

  • What can I do to lower my risk for side effects from Neulasta?
  • Are there other things I can do to manage side effects from Neulasta?
  • Are there any side effects from Neulasta that I’m at higher risk for?

To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.

Q:

My doctor prescribed Neulasta Onpro for me. What happens if it doesn’t give my dose correctly? Am I at higher risk for side effects if this happens?

Anonymous

A:

There have been reports of people who used Neulasta Onpro missing doses or receiving incomplete doses of medication. This was due to the on-body injector (OBI) not working correctly. If you miss a dose or receive an incomplete dose, you could be at higher risk for certain side effects. Examples include neutropenia (low level of neutrophils, a type of white blood cell), febrile neutropenia (neutropenia with a fever), and infection.

If you think your Neulasta Onpro device isn’t working as intended, contact your doctor right away.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.