Briumvi is a prescription medicine used to treat relapsing forms of multiple sclerosis (MS) in adults. Like all medications, it can cause side effects. If you are preparing to start treatment, it helps to know which reactions are most common, which ones are serious, and what to expect during and after each infusion.
This guide explains Briumvi side effects in clear terms so you can feel more prepared before your first infusion. If you are also reviewing treatment basics, you may want to read Briumvi treatment: What to Know Before Starting.
Table of Contents
What is Briumvi?
Briumvi (ublituximab-xiiy) is an infusion treatment for certain types of MS. It works by targeting specific B cells, which are part of the immune system and are involved in the inflammation that can damage the nervous system in MS.
Because Briumvi affects the immune system, its side effects often involve infusion reactions or a higher risk of infections. That is why Briumvi side effects deserve a careful review before treatment starts.
The treatment is given in a medical setting, so your care team can monitor you during the infusion and respond quickly if you develop symptoms. That close supervision is one reason many people feel more comfortable starting therapy after they understand the process.
The most common side effects
Many people tolerate Briumvi well, but some side effects are fairly common. The most frequently reported side effects include:
- Infusion reactions
- Upper respiratory tract infections, such as the common cold
- Fever
- Headache
- Rash
- Chills
- Fatigue
- Cough
- Nausea
These side effects are often mild to moderate, and some happen more often around the time of the infusion. For many patients, the pattern of Briumvi side effects becomes easier to predict after the first treatment.
It is also common for symptoms to overlap. For example, headache, tiredness, and mild nausea may all happen on the same day, especially after an infusion. When that happens, the symptoms do not always mean something is wrong, but they should still be mentioned to your healthcare team if they feel stronger than expected.
Infusion reactions: what to expect
One of the most important things to know about Briumvi is that it is given by intravenous infusion, which means into a vein. Infusion reactions are among the most common side effects.
Possible symptoms of an infusion reaction
These may include:
- Flushing
- Itching
- Rash
- Fever
- Chills
- Headache
- Nausea
- Trouble breathing
- Throat irritation
- Dizziness
- Low blood pressure
- Fast heartbeat
When do infusion reactions happen?
They usually happen during the infusion or within 24 hours afterward. For many people, the risk is highest with the first infusion. This is one of the most important parts of Briumvi side effects to understand before your appointment.
Some reactions are mild and brief, while others may last longer or feel more uncomfortable. Even if symptoms go away on their own, you should still tell your healthcare provider about them because the information can help guide future infusions.
How are infusion reactions managed?
Before each infusion, your healthcare team will usually give you premedications to lower the risk of reactions. These may include medicines such as:
- A corticosteroid
- An antihistamine
- Acetaminophen
Your infusion may also be given slowly at first so the team can watch for reactions and adjust the rate if needed. More details on dosing and treatment timing are available in the Briumvi Dosage Guide: What to Know Before Treatment.
If a reaction develops, the infusion may be paused, slowed, or restarted later depending on the severity of the symptoms. This is why infusion day monitoring is so important.
Infection risk with Briumvi
Because Briumvi changes how the immune system works, it can make it easier to get infections. This is one of the main longer-term safety concerns, and it is a key part of the overall Briumvi side effects profile.
Not every infection will be serious, but even common infections can feel more disruptive if your immune system is less able to respond. Paying attention to new symptoms early can help you get treated sooner if needed.
Common infections
People taking Briumvi may be more likely to develop:
- Common colds
- Sinus infections
- Bronchitis
- Other upper respiratory infections
- Urinary tract infections
These are the kinds of infections many people already know how to recognize, but they may last longer or feel more intense in some cases. If symptoms do not improve, it is worth checking in with your clinician.
Serious infections
In rare cases, Briumvi may increase the risk of more serious infections. Contact your healthcare provider right away if you develop symptoms such as:
- Fever that does not go away
- Shortness of breath
- Severe cough
- Burning with urination
- Confusion
- Unusual weakness
- Signs of a worsening infection
If you have an active infection before treatment, your doctor may delay your infusion until you recover.
To reduce avoidable risks, it helps to mention recent colds, dental infections, skin infections, or any illness that has not fully cleared up. That conversation can make a real difference in treatment planning.
Headache, fatigue, and flu-like symptoms
Some people feel tired, achy, or “off” after treatment. Headache and fatigue are among the side effects that can show up after an infusion. These are common Briumvi side effects that usually improve with time.
These symptoms are often temporary and may improve with rest, hydration, and over-the-counter symptom relief if approved by your doctor. A quiet rest day after treatment can also be helpful, especially after the first infusion.
Flu-like symptoms can be frustrating because they may resemble a minor illness. If you feel generally unwell for more than a short period, or if the symptoms get worse instead of better, it is a good idea to contact your care team.
Rash, itching, and skin-related effects
Skin reactions can happen with Briumvi, especially as part of an infusion reaction. These may include:
- Rash
- Itching
- Hives
- Redness
If you notice a mild rash after treatment, tell your healthcare provider. If the rash is accompanied by swelling, trouble breathing, or dizziness, seek urgent medical help.
Even when skin symptoms are mild, they are worth documenting because they can help your team decide whether any adjustments are needed before the next dose.
Nausea and stomach upset
Some people experience nausea during or after infusion. This is usually short-lived, but it can be uncomfortable.
Helpful steps may include:
- Eating a light meal before treatment if your care team says it is okay
- Drinking enough fluids
- Telling your provider if nausea becomes frequent or severe
If nausea is paired with vomiting, dizziness, or trouble keeping fluids down, the situation deserves prompt medical attention. Staying hydrated is especially important if you are also running a fever or dealing with another infection.
Are there serious side effects of Briumvi?
Yes, although serious side effects are less common. Important risks can include:
Severe infusion reactions
Rarely, infusion reactions can become serious and may require immediate medical treatment. Signs include:
- Trouble breathing
- Swelling of the face, lips, or throat
- Chest pain
- Very low blood pressure
- Fainting
Serious infections
As noted above, Briumvi can increase infection risk, including rare but serious infections.
Low immune defenses
Briumvi may lower certain immune cells and affect your body’s ability to fight infection. Your doctor may monitor you with blood tests before and during treatment.
This monitoring is part of why doctors can catch changes early. It also helps them decide whether it is safe to continue treatment on schedule or whether a delay makes more sense.
Liver problems
Although not the most common concern, liver-related issues can occur with some immune therapies. Report symptoms such as:
- Yellowing of the skin or eyes
- Dark urine
- Severe fatigue
- Pain in the upper right side of the abdomen
Progressive multifocal leukoencephalopathy (PML)
PML is a rare but serious brain infection that has been associated with some immune-targeting MS therapies. While it is uncommon, any new or worsening neurological symptoms should be reported quickly.
Symptoms to watch for may include:
- Confusion
- Memory problems
- Vision changes
- Weakness on one side of the body
- Trouble speaking or walking
For a broader overview of MS medicine warnings and monitoring, the National MS Society medication resource offers helpful general information.
Serious problems are uncommon, but they should never be ignored. If a symptom feels sudden, severe, or clearly unusual for you, it is better to ask for help sooner rather than later.
What side effects happen right after the first infusion?
The first infusion is often the time when side effects are most likely to appear. Common immediate effects include:
- Flushing
- Itching
- Headache
- Chills
- Fever
- Nausea
- Fatigue
This is why the infusion is closely monitored. Your care team will watch for reactions and may slow or pause the infusion if needed. In many cases, the first-day pattern of Briumvi side effects gives your team useful information for future infusions.
Some people feel fine during the infusion but notice symptoms later that day or the next day. Others may feel tired for a day or two afterward without having any major reaction. Both patterns can happen, and your experience with the first dose may not be exactly the same as what happens later.
What side effects can happen later?
Some side effects show up after the infusion day rather than during treatment. These may include:
- Delayed infusion reactions
- Fatigue
- Headache
- Mild flu-like symptoms
- Infection symptoms in the days or weeks after treatment
If you feel unwell after an infusion, it is important to tell your healthcare provider, especially if symptoms are worsening instead of improving.
Later symptoms can be easy to dismiss, particularly if they seem mild at first. Tracking the timing, severity, and duration of symptoms can make it easier to tell whether the issue is part of the expected recovery period or something that needs a closer look.
Who may be at higher risk for side effects?
Some people may have a greater chance of complications from Briumvi, including those who:
- Have a current infection
- Have a history of frequent infections
- Are taking other immune-suppressing medicines
- Have liver problems
- Have had severe reactions to infusion therapies before
- Are pregnant, planning pregnancy, or breastfeeding
Your doctor will review your health history to determine whether Briumvi is appropriate for you.
This review may also include your vaccination history, recent lab work, and any past issues with immune-related medicines. Those details help your provider judge whether the benefits of treatment outweigh the possible risks.
What will your doctor check before starting Briumvi?
Before the first dose, your healthcare provider may order tests or ask questions about your health to reduce the risk of complications. This may include:
- Screening for hepatitis B
- Checking for active infections
- Reviewing vaccination history
- Blood tests to assess immune function and general health
- Discussing other medicines you take
This screening matters because some infections can become more serious when the immune system is affected. The U.S. Food and Drug Administration also publishes official prescribing information for Briumvi at FDA drug information, which can be useful for reviewing safety details.
Your doctor may also ask about symptoms that seem unrelated at first, such as persistent cough, skin changes, or unusual fatigue. Those details can matter more than many people realize when planning treatment safely.
Can you get vaccines before Briumvi?
Vaccination planning is important before starting Briumvi. Certain vaccines may need to be given before treatment begins, especially live vaccines. Once treatment starts, some vaccines may not work as well or may not be recommended.
Talk to your doctor early if you need any vaccines so the timing can be planned safely.
This is another reason to bring up your complete medical schedule before treatment. If you need a routine booster, travel vaccine, or catch-up immunization, it is usually easier to plan ahead than to fix the timing later.
How long do Briumvi side effects last?
It depends on the side effect.
- Infusion reactions: often happen during infusion or within a day and then resolve
- Headache, fatigue, nausea: usually temporary
- Infections: can last longer and may require treatment
- Immune-related effects: may continue to affect your body throughout therapy
If a side effect lasts more than a short time or keeps coming back, it should be discussed with your healthcare team.
It is also important to remember that the same symptom can mean different things at different times. A headache right after infusion may be part of the treatment reaction, while a headache that appears with fever or neck stiffness could point to something else. That is why context matters.
When should you call a doctor?
Contact your healthcare provider if you have:
- Fever
- Signs of infection
- A rash that spreads or gets worse
- Persistent nausea or headache
- Trouble breathing
- Chest pain
- Swelling of the face or throat
- New weakness, vision changes, or confusion
- Any symptom that feels severe or unusual
Call emergency services right away if you have signs of a severe allergic or infusion reaction.
When in doubt, err on the side of reporting symptoms. Even if the issue turns out to be minor, your medical team would usually rather hear about it early than after it becomes more difficult to manage.
How to prepare for Briumvi side effects
A little preparation can make treatment easier. Before your infusion:
- Tell your doctor about all medicines and supplements you take
- Report any recent illness or infection
- Ask about premedications
- Wear comfortable clothing
- Arrange for transportation if you think you may feel tired afterward
- Drink fluids unless your doctor tells you otherwise
Knowing what to expect can help reduce anxiety and make the experience smoother. It can also help you recognize which Briumvi side effects are common and which ones should be reported right away.
Some people also find it helpful to bring a water bottle, a light snack, headphones, or something to read during the infusion visit. Small comforts do not prevent side effects, but they can make the experience easier.
When to track symptoms at home
After treatment, it can help to keep a simple note of how you feel for the first day or two. Write down the time symptoms begin, how long they last, and whether they improve or worsen. This is especially useful if you have a delayed reaction or if you are trying to tell the difference between normal post-infusion fatigue and a problem that needs medical attention.
Tracking symptoms can also help your care team decide whether your premedications, infusion speed, or monitoring plan should change for the next appointment.
You do not need a complicated symptom diary. A short list in your phone, a calendar note, or a paper log is enough if it clearly shows what happened and when.
Questions to ask your healthcare provider
Before starting treatment, consider asking:
- Which side effects are most likely for me?
- What symptoms should I report immediately?
- Will I need blood tests or infection screening?
- Should I change any of my medicines before the infusion?
- How long should I plan to stay at the infusion center?
- What should I do if I develop a fever after treatment?
These questions can make it easier to understand your personal risk and what to expect from Briumvi side effects over time.
You may also want to ask how the clinic wants you to communicate after treatment if symptoms appear at home. Having that plan in advance can save time and reduce stress.
The bottom line
Briumvi Side Effects are often manageable, but it is important to understand the most common ones before treatment begins. The biggest things to expect are infusion reactions, mild flu-like symptoms, and a higher risk of infections. Serious side effects are less common, but they do require prompt medical attention.
If you are starting Briumvi, ask your healthcare provider about your individual risk, what symptoms to watch for, and how to prepare for your infusion day. Being informed is one of the best ways to stay safe and confident throughout treatment.
For official safety details and prescribing information, review the FDA drug information page before your appointment. That extra step can help you better understand the benefits and possible risks before treatment begins.
