Baloxavir marboxil (By mouth)

Baloxavir Marboxil (bal-OX-a-vir mar-BOX-il)

Treats influenza (flu).

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to baloxavir marboxil.

How to Use This Medicine:


  • Your doctor will tell you how much medicine to use. Do not use more than directed. Do not take this medicine for any illness other than the flu.
  • Start using this medicine within 48 hours, as soon as the symptoms of flu (including cough, fever, runny nose, headache, joint or muscle pain) appear.
  • Take this medicine with or without food. However, do not take this medicine with dairy products or drinks rich in calcium.
  • Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.
  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.
  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Do not use this medicine together with antacids, laxatives, or oral supplements containing calcium, iron, magnesium, selenium, or zinc.
  • Do not use this medicine if you have received the nasal flu vaccine (live attenuated influenza vaccine), unless your doctor says it is okay.

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have any type of infection.
  • This medicine is not a substitute for a yearly flu shot. It also will not treat or prevent a bacterial infection.
  • Call your doctor if your symptoms do not improve or if they get worse.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Blistering, peeling, or loose skin
  • Chest tightness, trouble breathing
  • Cough, fever, headache, pain or tenderness around your eyes and cheekbones

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 11/6/2020

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites.

All rights reserved

A.D.A.M. content is best viewed in IE9 or above, Firefox and chrome browser.