What Is Xofluza 40 Mg Dose Pack? Uses, Dosage, and What You Need to Know in 2026

What Is Xofluza 40 Mg Dose Pack?

Xofluza 40 Mg Dose Pack is a brand-name prescription antiviral medication used to treat the flu (influenza). Its generic name is Baloxavir Marboxil, and it is made by Genentech, a member of the Roche Group.

What makes Xofluza unique is that it's a single-dose treatment. You take one dose by mouth, and that's it — no pills to remember for five days. It was approved by the FDA in 2018 and represents a different class of antiviral than older medications like Oseltamivir (Tamiflu).

Xofluza belongs to a class called cap-dependent endonuclease inhibitors. In simpler terms, it works by blocking a specific enzyme the flu virus needs to copy itself inside your cells. For a deeper look at how this works, see our article on how Xofluza works.

What Does Xofluza Treat?

Xofluza 40 Mg Dose Pack is FDA-approved for two uses:

1. Treatment of acute, uncomplicated influenza — For patients 5 years of age and older who have had flu symptoms for no more than 48 hours
2. Post-exposure prophylaxis (prevention) — For patients 5 years and older who have been in close contact with someone who has the flu

Xofluza works against both influenza A and influenza B viruses. It does not treat the common cold, COVID-19, or other respiratory infections.

How to Take Xofluza 40 Mg Dose Pack

Taking Xofluza correctly is important for it to work effectively. Here are the key instructions:

• Take it as a single oral dose — One time, and you're done
• Take it within 48 hours of the start of your flu symptoms
• Take it on an empty stomach — Or with a non-dairy, non-calcium-fortified snack
• Do NOT take with dairy products — Milk, cheese, yogurt, and calcium-fortified beverages can reduce the drug's effectiveness
• Avoid polyvalent cation-containing products — This includes supplements with calcium, iron, magnesium, selenium, or zinc, as well as certain antacids and laxatives

For a complete list of what to avoid, read our article on Xofluza drug interactions.

Dosage: How Much Xofluza Do You Take?

Xofluza dosing is based on body weight, not age. Here's how it breaks down:

• 20 kg to less than 40 kg (about 44 to 88 lbs): 20 mg single dose
• 40 kg to less than 80 kg (about 88 to 176 lbs): 40 mg single dose — this is the Xofluza 40 Mg Dose Pack
• 80 kg and above (176 lbs and above): 80 mg single dose (two 40 mg tablets)

Your doctor will determine the right dose based on your weight. If you weigh 80 kg or more, you may need two tablets from the 40 mg dose pack.

Who Can Take Xofluza?

Xofluza is approved for patients 5 years of age and older who weigh at least 20 kg (about 44 lbs). This includes children, teens, adults, and older adults.

Special Populations

• Pregnant women — Limited data is available. Use only if the potential benefit justifies the risk. Talk to your doctor.
• Breastfeeding women — Not recommended without consulting your doctor first.
• Liver problems — Xofluza has not been studied in patients with severe liver disease.
• Immunocompromised patients — Sometimes used off-label, occasionally in combination with Oseltamivir. Consult your doctor.

Who Should NOT Take Xofluza?

You should not take Xofluza 40 Mg Dose Pack if you are allergic to Baloxavir Marboxil or any ingredient in the medication. There is no boxed warning for Xofluza, but always tell your doctor about any allergies before starting any new medication.

How Does Xofluza Compare to Tamiflu?

Both Xofluza and Oseltamivir (Tamiflu) are prescription antiviral medications for the flu. Here are the key differences:

• Dosing — Xofluza is one dose; Tamiflu is taken twice daily for five days
• Mechanism — Xofluza blocks viral mRNA synthesis; Tamiflu inhibits neuraminidase (a different viral enzyme)
• Availability — Tamiflu (and its generic) is more widely stocked at pharmacies
• Generic — Tamiflu has a generic version; Xofluza does not as of 2026
• Cost — Xofluza typically costs $150-$200 without insurance; generic Oseltamivir is often less expensive

For a full comparison of options, read our guide: Alternatives to Xofluza 40 Mg Dose Pack.

What Does Xofluza 40 Mg Dose Pack Cost?

Without insurance, Xofluza 40 Mg Dose Pack typically costs between $150 and $200. There is no generic version available as of 2026.

However, there are ways to save:

• Genentech Savings Card — May lower your cost to as low as $30 with commercial insurance
• Genentech Patient Foundation — Provides Xofluza for free to eligible uninsured or underinsured patients
• Pharmacy discount cards — SingleCare, GoodRx, and others may offer savings

For a complete breakdown of savings options, see: How to save money on Xofluza 40 Mg Dose Pack.

Is Xofluza Hard to Find?

Xofluza can sometimes be difficult to find at retail pharmacies, especially during peak flu season. Because it's a single-dose, seasonal medication, many pharmacies don't stock it routinely. If you're having trouble finding it, read our guides:

• Why Xofluza is hard to find in 2026
• How to find Xofluza in stock near you
• How to check pharmacy stock without calling

You can also use MedFinder to search for pharmacies that currently have Xofluza available in your area.

Common Side Effects

Like all medications, Xofluza can cause side effects. The most common include:

• Diarrhea
• Bronchitis
• Nausea
• Sinusitis
• Headache

Most side effects are mild and short-lived. For detailed information, read our article on Xofluza side effects.

Key Takeaways

• Xofluza 40 Mg Dose Pack (Baloxavir Marboxil) is a single-dose prescription antiviral for influenza
• It's approved for treatment and prevention in patients 5 years and older
• Dosing is based on body weight — 40 mg is for patients 40 kg to less than 80 kg
• Take on an empty stomach; avoid dairy, calcium-fortified beverages, and mineral supplements
• Must be taken within 48 hours of symptom onset
• No generic is available as of 2026, but savings programs exist

Need a prescription? Learn how to find a doctor who can prescribe Xofluza near you.