5 Side Effects of Xofluza and How to Manage Them

You have a fever, cough, and severe muscle aches. If it’s between the months of October and May in the U.S., there’s a chance you might have the flu. After seeing a healthcare professional, they might prescribe you Xofluza (baloxavir marboxil).

Xofluza is an antiviral medication that can help treat or prevent the flu with a single dose. But even though you only take one dose, side effects are still possible.

Xofluza side effects at a glance

Before diving into details about Xofluza side effects, it’s important to note that most people can take it without any problems. In fact, side effects were reported more often in clinical trials by people who took a placebo (a pill with no medicine in it) than by those who took Xofluza.

Some of the side effects we’ll discuss below are also symptoms of the flu. So it’s also possible what you’re experiencing is coming from the illness and not the medication. But if anything feels excessive or severe, it never hurts to discuss it with your healthcare team.

Mild Xofluza side effects include:

• Diarrhea

• Bronchitis (tight airways)

• Nausea

• Vomiting

• Sinusitis (swollen sinuses)

• Headache

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Serious side effects with Xofluza are very rare. But some people have reported allergic reactions while taking the medication. Contact your prescriber if you notice any of the following after taking Xofluza:

• Hives

• Rash

• Itching

• Wheezing

These are symptoms of a possible allergic reaction. If you experience symptoms that are severe or life-threatening, such as trouble breathing, call 911 or go to the nearest ER.

Below are details on five potential Xofluza side effects, plus tips for managing them.

1. Diarrhea

Diarrhea is a mild Xofluza side effect. But it’s also a possible symptom of the flu, especially for kids. So it can be hard to tell what’s causing loose stools.

Regardless of the reason, there are ways you can manage diarrhea at home:

• Drink plenty of fluids to stay hydrated.

• Avoid beverages that can worsen diarrhea, such as milk, alcohol, and caffeinated drinks.

• Avoid fatty, spicy, or fried foods.

• Eat yogurt or drink kefir (a fermented milk-based drink).

• Ask a healthcare professional if you can safely take over-the-counter (OTC) anti-diarrhea medications, such as loperamide (Imodium A-D).

EXPERT PICKS: WHAT TO READ NEXT

• How does Xofluza work? Pharmacists answer this and other frequently asked questions about Xolfuza (baloxavir marboxil).

• Tips for taking Xofluza: Read these pharmacist-backed tips for taking Xofluza to help you get the most from your medication.

• Xofluza vs. Tamiflu (oseltamivir): Find out how these two flu treatments compare.

If Xofluza is causing diarrhea, it should resolve on its own within the days following your dose. If you experience severe diarrhea, or it doesn’t improve within a few days, contact your healthcare team. This isn’t typical.

2. Bronchitis

Bronchitis occurs when your airways are inflamed (swollen). This usually causes you to cough and can make it harder to breathe. In studies, some people reported bronchitis as a Xofluza side effect. But it’s also a possible complication of the flu. So it could continue until your body recovers from your illness.

OTC cough medications, such as Mucinex DM (guaifenesin / dextromethorphan), can help relieve bronchitis for some people. Using a humidifier may also ease this sensation. If these options don’t work well enough, contact a healthcare professional. They may prescribe you a prescription cough medication or an inhaler, such as albuterol (Ventolin HFA).

3. Nausea

No one likes feeling sick to their stomach. So you should be aware that nausea is a possible Xofluza side effect. This is typically a mild side effect, but it can be frustrating. For children, vomiting is also a possible Xofluza side effect. Keep in mind that the flu can sometimes cause nausea and vomiting, particularly for children. So these symptoms may not be related to Xofluza.

Taking Xofluza with food can help prevent nausea. So if you tend to be sensitive to stomach side effects with other medications, take your dose with food. Just avoid taking Xofluza with foods that contain calcium, such as dairy products. These can affect how well your body absorbs the medication.

4. Sinusitis

Sinusitis is another potential Xofluza side effect. Sinusitis is inflammation of your sinuses (spaces in the bones around your forehead and nose). It can cause pressure and pain around your face. It can also make your nose feel stuffy. If you’ve ever had a sinus infection, then you know how uncomfortable and painful it can be.

But as with the side effects above, the flu itself can also cause sinusitis. So it can be hard to tell if what you’re feeling is coming from the medication or the infection.

If you experience sinusitis after taking Xofluza, there are a few things that may help relieve it:

• OTC pain relievers, such as ibuprofen (Advil, Motrin), can help with sinus pain. But these medications aren’t safe for everyone. So ask a healthcare professional before taking them.

• Saline (salt water) nasal rinses, such as a neti pot, can help flush excess mucus out of the sinuses. Just be sure to use distilled water (not tap water) when preparing it.

• Corticosteroid (steroid) nasal sprays, such as fluticasone (Flonase), can also help relieve congestion. But they take a few days of consistent use to start working.

• Nasal spray decongestants, such as oxymetazoline (Afrin), can help shrink blood vessels in the nose and sinuses. This makes it easier to breathe. They start working within a few minutes. But you shouldn’t use them for more than 3 days in a row. Using them longer than this can actually worsen your congestion.

• Oral decongestants, such as pseudoephedrine (Sudafed), work similarly to nasal decongestants. They take about 30 to 60 minutes to start working. But you shouldn’t take them for more than 7 days in a row. And it’s recommended to avoid them if you have high blood pressure or other heart conditions.

If sinusitis doesn’t improve with OTC treatments, contact a healthcare professional.

5. Headaches

Many medications can cause headaches. While very uncommon, Xofluza may also cause this side effect. Keep in mind that headache is also a common symptom of the flu. If your headache is a result of Xofluza, it should be fast-passing. If your headache is due to the flu, it might continue until you’re feeling better.

If you do experience a headache after taking Xofluza, there are options to help:

• Drink more water.

• Rest in a dark, quiet room.

• Try to maintain your usual bedtime routine and schedule, prioritizing good sleep hygiene.

• Place an ice pack or cool compress where you feel pain.

• Avoid alcohol and limit caffeine.

Ask your healthcare team if you can safely take OTC pain relievers, such as ibuprofen and acetaminophen (Tylenol).

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Written by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Samantha Kasting, PharmD Candidate

Samantha Kasting, PharmD Candidate, has 4.5 years of hospital pharmacy experience. She has worked at St. Louis Children’s Hospital inpatient pharmacy since 2021.

Reviewed by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

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