Understanding Xofluza 40 Mg Dose Pack Side Effects

If your doctor has prescribed Xofluza 40 Mg Dose Pack (Baloxavir Marboxil) for the flu, you may be wondering what side effects to expect. The good news is that Xofluza is generally well-tolerated, and because it's a single-dose medication, any side effects tend to be brief.

This article covers the most common side effects, the rare but serious ones to watch for, and clear guidance on when you should call your doctor. If you're still learning about this medication, start with our overview: What is Xofluza 40 Mg Dose Pack?

Common Side Effects of Xofluza 40 Mg Dose Pack

In clinical trials, the following side effects were reported most frequently. Keep in mind that some of these overlap with flu symptoms themselves, which can make it hard to tell what's caused by the medication versus the illness.

Diarrhea

Diarrhea is the most commonly reported side effect of Xofluza. It's usually mild and resolves on its own within a day or two. To manage it:

• Stay hydrated — drink water, broth, or electrolyte drinks
• Avoid dairy products, caffeine, and greasy foods until it passes
• Contact your doctor if diarrhea is severe or lasts more than 2-3 days

Nausea

Some people feel nauseous after taking Xofluza. This is usually mild and temporary. Taking the medication with a light, non-dairy snack may help. Remember — you should not take Xofluza with dairy products or calcium-fortified beverages, as these can reduce the drug's effectiveness. For more on what to avoid, see our article on Xofluza drug interactions.

Bronchitis

Bronchitis (inflammation of the airways) has been reported in some patients taking Xofluza. This may be related to the flu itself rather than the medication. Symptoms include coughing, chest tightness, and mucus production. If your cough worsens significantly after taking Xofluza, let your doctor know.

Sinusitis

Sinus inflammation or infection has also been reported. Again, this may be a complication of the flu rather than a direct side effect of the medication. Symptoms include facial pain, pressure, and nasal congestion.

Headache

Headaches are common both as a flu symptom and as a side effect of Xofluza. Over-the-counter pain relievers like Acetaminophen (Tylenol) or Ibuprofen (Advil) can help. These do not interact with Xofluza.

Serious Side Effects: When to Seek Immediate Help

Serious side effects from Xofluza 40 Mg Dose Pack are rare, but they can happen. You should seek medical attention right away if you experience any of the following:

Severe Allergic Reactions (Anaphylaxis)

Although extremely rare, anaphylaxis has been reported with Xofluza. Call 911 or go to the emergency room immediately if you experience:

• Difficulty breathing or swallowing
• Swelling of the face, lips, tongue, or throat
• Severe rash or hives
• Rapid heartbeat
• Dizziness or fainting

If you have a known allergy to Baloxavir Marboxil or any ingredient in Xofluza, do not take this medication.

Secondary Bacterial Infections

The flu can sometimes lead to bacterial infections like pneumonia. While this isn't a direct side effect of Xofluza, you should contact your doctor if:

• Your symptoms get worse after initially improving
• You develop a high fever after your flu symptoms had started to get better
• You have difficulty breathing, chest pain, or a persistent cough with colored mucus

Side Effects vs. Flu Symptoms: How to Tell the Difference

One challenge with flu medications is that many side effects look a lot like the flu itself. Here's a quick comparison:

• Diarrhea — More likely a side effect if it starts shortly after taking Xofluza and you didn't have it before
• Nausea — Could be either; if it's new after taking the dose, it may be medication-related
• Headache — Very common with the flu; hard to attribute to the medication alone
• Fatigue — Almost always the flu; Xofluza doesn't typically cause tiredness

If you're unsure whether what you're feeling is from the flu or from Xofluza, err on the side of caution and call your doctor.

How Long Do Side Effects Last?

Because Xofluza 40 Mg Dose Pack is taken as a single dose, side effects are generally short-lived. Most common side effects resolve within 1-3 days. The medication has a long half-life in the body (about 79 hours), which means the drug stays active for several days — but this also means you don't need to take any additional doses.

If side effects persist beyond 3-4 days, or if they worsen over time, contact your healthcare provider.

Who May Be More Likely to Experience Side Effects?

Certain groups may want to be extra cautious:

• People with weakened immune systems — May experience different or prolonged side effects
• Pregnant or breastfeeding women — Limited data is available; discuss risks with your doctor
• People taking supplements with calcium, iron, magnesium, selenium, or zinc — These don't cause more side effects, but they reduce the drug's effectiveness, which could mean your flu lasts longer

For more details on who should and shouldn't take Xofluza, read our article on Xofluza uses and dosage.

What to Do If You Experience Side Effects

Here's a simple action plan:

1. Mild side effects (diarrhea, nausea, headache) — Stay hydrated, rest, and monitor. These usually pass quickly.
2. Moderate side effects (persistent vomiting, worsening cough, sinus pain) — Call your doctor's office or a nurse hotline for advice.
3. Severe side effects (allergic reaction symptoms, difficulty breathing, high fever returning) — Call 911 or go to the emergency room immediately.

Comparing Side Effects: Xofluza vs. Tamiflu

If you're weighing Xofluza against other flu treatments, here's how side effects compare to Oseltamivir (Tamiflu):

• Xofluza — Most common: diarrhea, bronchitis, nausea, sinusitis, headache
• Tamiflu — Most common: nausea, vomiting, headache, pain

Both medications are generally well-tolerated. The main advantage of Xofluza is that it's a single dose, so you're not taking medication for five days. For a detailed comparison, see our guide on alternatives to Xofluza 40 Mg Dose Pack.

Key Takeaways

• Common side effects of Xofluza 40 Mg Dose Pack include diarrhea, nausea, bronchitis, sinusitis, and headache
• Most side effects are mild and resolve within 1-3 days
• Serious allergic reactions are rare but require immediate medical attention
• Many side effects overlap with flu symptoms — when in doubt, call your doctor
• Xofluza is a single-dose treatment, so side effects tend to be short-lived

If you're ready to fill your prescription, learn how to check if a pharmacy has Xofluza in stock or use MedFinder to search for availability near you. Concerned about the price? Check out our guide on saving money on Xofluza 40 Mg Dose Pack.