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 provider, you might leave their office with a prescription for 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.

5 Xofluza side effects to know about

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.

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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 provider.

1. Diarrhea

Diarrhea is defined as more than three watery stools in a single day. And it can be very uncomfortable. In Xofluza’s clinical trials, about 3% of people reported experiencing diarrhea.

If you experience loose stools after taking Xofluza, be sure to stay hydrated. You may find a bland diet is helpful until it passes. You can also try over-the-counter (OTC) diarrhea medications to help relieve this side effect.

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, 3% of people reported bronchitis as a Xofluza side effect. But it’s also a common symptom 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. Using a humidifier may also ease this sensation. If these options don’t work well enough, contact your healthcare provider. They may prescribe you a prescription cough medication or an inhaler, like Ventolin (albuterol).

3. Nausea

No one likes feeling sick to their stomach. So you should be aware that nausea is a possible Xofluza side effect. In clinical trials, 2% of people taking Xofluza reported it. This is typically a mild side effect, but it can be frustrating. In children, vomiting is also a common Xofluza side effect, happening to 5% of children in clinical trials.

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 listed Xofluza side effect that 2% of people reported in clinical trials. 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.

If you experience sinusitis after taking Xofluza, there are a few things that may help relieve it. OTC pain relievers, like ibuprofen (Advil, Motrin), can help with sinus pain. You can also try saline nasal washes and decongestants.

5. Headaches

Many medications can cause headaches. While only reported by 1% of people in studies, 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. OTC pain relievers, like acetaminophen (Tylenol) or ibuprofen, are popular choices for headache relief. Drinking plenty of water, resting, and avoiding loud noises can also help ease headache pain.

When should I contact my healthcare provider about Xofluza side effects?

Xofluza side effects should be mild. So if you’re experiencing severe side effects, contact your healthcare provider. Remember, things like headaches and bronchitis are common flu symptoms. So it’s possible they’re not coming from the medication.

You should also speak with a healthcare provider if you believe you’re having an allergic reaction to Xofluza. Allergy symptoms can be mild, like rash or hives. But they can also be very serious, like breathing difficulties. If you notice swelling of the face or throat or have trouble breathing, call 911 or go to the nearest emergency room.

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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:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

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