How Long Does Rituxan Stay in Your System? Plus, Answers to 4 More Rituxan FAQs

You could say that Rituxan (rituximab) is a bit of a trendsetter in the field of oncology. It’s like the little black dress of targeted therapy — classic, versatile, and still relevant after all these years. 

Rituxan was actually the first monoclonal antibody FDA-approved for use in cancer. Monoclonal antibodies are laboratory-made medications that attach to specific targets on problematic cells and destroy them. Compared with nonspecific treatments such as chemotherapy, medications like Rituxan are intended to be more targeted in their approach and have a more tolerable side effect profile.

If you’ve been diagnosed with a blood cancer or autoimmune condition, there’s a good chance you might encounter Rituxan at some point. We’ll answer some of the top questions asked about Rituxan so you can feel prepared for your treatment.

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1. How long does Rituxan stay in your system?

Rituxan stays in your system anywhere from 3 to 6 months after your last infusion. But its effects can last even longer. This is because Rituxan fights off white blood cells in your immune system called B cells. These cells normally make proteins called antibodies, which fight off foreign invaders such as bacteria and viruses.

After you stop receiving Rituxan, it takes time for your body to make enough B cells to match the amount you had before treatment. When you have fewer B cells, it’s harder to fight an infection. Most people start making B cells around 6 months after stopping treatment. And you can expect a return to pre-Rituxan levels by about 12 months. 

Good to know: Vaccines might be less effective if you receive them within 6 months of your last Rituxan dose. And if you’re thinking about getting pregnant, you should wait at least 12 months after your last Rituxan dose, just to be safe.

2. What is Rituxan used for?

Rituxan has two main uses — certain blood cancers that make too many B cells (B-cell lymphomas) and autoimmune conditions. Here’s a quick summary.

With B-cell lymphomas, unhealthy B cells grow out of control and crowd out healthy cells. These cancer cells collect in your lymph nodes.

Autoimmune conditions happen when your body’s B cells incorrectly identify your own body as a foreign invader, resulting in inflammation and damage to certain body parts.

Do Rituxan biosimilars treat the same things as Rituxan?

Rituxan biosimilars are biologic medications that are very similar to Rituxan. They’re expected to have the same benefits and side effects. But they are not exactly the same. They’re created to make medications such as Rituxan easier to access and more affordable. 

Rituxan currently has three biosimilars available, including:

• Truxima (rituximab-abbs)

• Ruxience (rituximab-pvvr)

• Riabni (rituximab-arrx)

3. Is Rituxan chemotherapy or immunotherapy?

Rituxan is a type of immunotherapy. It’s not considered chemotherapy.

How does Rituxan work?

Rituxan attaches to a protein on the surface of B cells called CD20. This protein is found on fully developed, healthy B cells and cancer-causing B cells. Once Rituxan attaches to CD20, it recruits your immune system to destroy these cells. 

However, CD20 is not found on healthy B cells that are still growing (immature B cells). This way, you always have a reserve of healthy B cells to replace the ones that were destroyed once you stop receiving Rituxan.

Rtiuxan works in the same way for autoimmune conditions. But in these cases, Rituxan destroys B cells that are sending incorrect messages to your immune system. This helps stop your body from attacking healthy tissue.

4. What’s a normal Rituxan dosage?

A typical Rituxan dosage depends on whether you’re being treated for blood cancer or an autoimmune condition.

For B-cell lymphomas, the most common Rituxan dosage is 375 mg/m². This type of dose is a common strategy for cancer medications; it takes into account both your height and your body weight (body surface area). When used alone, it can be given weekly. But when it’s given with chemotherapy, it’s typically given every 3 to 4 weeks. 

When Rituxan is given for autoimmune conditions, a flat dose of 500 mg to 1,000 mg is often used.

In either case, Rituxan is given as either an infusion in your vein (IV) or as an injection under the skin (called Rituxan Hycela). You can only receive Rituxan Hycela if you’ve received at least one IV dose of Rituxan without experiencing any major issues.

Good to know: Rituxan dosages are more complicated when it’s used for pediatric NHL. In addition, your dose might vary based on your situation. It’s best to discuss Rituxan’s dosing and frequency with your healthcare team so they can explain it in more detail.

5. What are the side effects of Rituxan?

The most common Rituxan side effects include:

• Infusion-related reactions

• Infections

• Body aches

• Tiredness

• Nausea

• Swelling

• Joint aches

• Diarrhea 

• Muscle spasms

Rituxan also has a boxed warning for serious infusion-related reactions, severe mouth sores, hepatitis B virus reactivation, and a rare neurologic disorder called progressive multifocal leukoencephalopathy (PML). A boxed warning is the strongest warning the FDA can give a medication. However, these serious risks are less common than its more standard side effects. There aren’t really any Rituxan interactions that contribute to side effects, either.

Infusion reactions

Infusion reactions are one of the most common side effects caused by Rituxan. They’re most likely to happen with your first infusion. And they typically happen within 30 minutes to 2 hours of starting your infusion. Symptoms of infusion-related reactions include chills, hives, and shortness of breath, among others.

However, the boxed warning is for severe infusion reactions, which aren’t as common. About 1 in 10 people experience a severe infusion reaction. Issues such as facial swelling, lung problems, and heart changes have been reported.

Hepatitis B reactivation

Your healthcare team will test your blood to see if you have a history of hepatitis B. Rituxan may prompt a previous hepatitis B infection to surface again. Uncontrolled hepatitis B infection can cause serious liver damage.

If you’re found to have a history of hepatitis B that you weren’t aware of, your healthcare team will likely prescribe you an antiviral medication such as Baraclude (entecavir) while you’re receiving Rituxan.

Progressive multifocal leukoencephalopathy

PML is a rare condition that attacks the protective layer of the nerves in your brain. It’s caused by a virus called polyomavirus JC. Most people have this virus in their bodies. But it only becomes a problem when your immune system is no longer able to fight the virus — such as in the case of Rituxan treatment. PML is more treatable if it’s caught early.

Tumor lysis syndrome 

Tumor lysis syndrome (TLS) happens when tumor cells are rapidly destroyed and release what’s inside of them into the blood. This can be a dangerous situation, causing high potassium and uric acid levels. This can in turn cause kidney and heart problems. 

The risk of TLS depends on the type of cancer you have and how advanced it is. Your healthcare team will closely monitor you and may decide to give you extra fluids or medications to prevent TLS. 

Contact your healthcare team immediately if you develop any of the following side effects:

• Mouth sores

• Peeling or blistering skin

• Changes in your vision, speech, or memory

• Abnormal heartbeat

• Changes in urination or bowel movements

• Stomach pain

• Uncontrolled nausea/vomiting

• Fever

Can I drive home after a Rituxan infusion?

You shouldn’t drive yourself home after your first Rituxan infusion. There is a small chance you could experience an infusion reaction as late as 24 hours after you receive it. 

In addition, certain medications that you receive before your Rituxan infusion, such as Benadryl (diphenhydramine) can make you sleepy. Talk with your healthcare team about whether you should arrange for a ride after your infusion.

How to save on Rituxan

There are ways to save on Rituxan. GoodRx can help you navigate between copay savings cards and patient assistance programs to save money on your prescription.

• Save with a copay savings card. If you have commercial insurance, you may be eligible to pay as little as $0 for Rituxan using a savings card from the manufacturer. Rituxan Hycela may also be as little as $0 with a manufacturer savings card.

• Save with patient assistance programs. If you’re uninsured or underinsured, you may be eligible for a Rituxan or Rituxan Hycela patient assistance program, which offer the medications free of charge.

You may also be able to save with a Rituxan biosimilar. Your healthcare team and insurance plan team (if applicable) can tell you if your out-of-pocket cost may be lower with Truxima, Ruxience, or Riabni.

Why trust our experts?

Written by:

Rachel Feaster, PharmD, BCOP, BCPS

Rachel Feaster has over 10 years of professional experience in ambulatory, inpatient, pharmacogenomics, and oncology care. She is board certified in oncology and pharmacotherapy.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Vanessa Carranza, PharmD

Vanessa Carranza, PharmD, is a pharmacist who has dedicated her career to the advancement of medical education for healthcare providers, patients, and caregivers, most notably in the oncology space.

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