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Xofluza Side Effects

Generic name: baloxavir marboxil

Medically reviewed by Last updated on Jan 17, 2021.

Note: This document contains side effect information about baloxavir marboxil. Some of the dosage forms listed on this page may not apply to the brand name Xofluza.

For the Consumer

Applies to baloxavir marboxil: oral tablet

Side effects requiring immediate medical attention

Along with its needed effects, baloxavir marboxil (the active ingredient contained in Xofluza) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking baloxavir marboxil:

Less common

  • Cough producing mucus
  • difficulty breathing
  • fever
  • headache
  • muscle aches
  • sore throat
  • stuffy or runny nose
  • tightness in the chest
  • unusual tiredness or weakness

Incidence not known

  • Blistering, peeling, or loosening of the skin
  • bloody, black, or tarry stools
  • chills
  • cough
  • diarrhea
  • difficulty swallowing
  • dizziness
  • fast heartbeat
  • hives, itching, skin rash
  • hoarseness
  • joint or muscle pain
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • red, irritated eyes
  • sores, ulcers, or white spots in the mouth or on the lips
  • voice changes

Side effects not requiring immediate medical attention

Some side effects of baloxavir marboxil may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

Incidence not known

  • Seeing, hearing, or feeling things that are not there
  • vomiting

For Healthcare Professionals

Applies to baloxavir marboxil: oral tablet


Common (1% to 10%): Diarrhea, nausea

Postmarketing reports: Vomiting, hematochezia, bloody diarrhea, melena, colitis, ischemic colitis[Ref]

Nausea was reported in 6% of elderly subjects compared to 1% of younger subjects (aged 18 to 64 years).[Ref]


Common (1% to 10%): Bronchitis, sinusitis, nasopharyngitis

Frequency not reported: Dysphonia[Ref]

Nervous system

Common (1% to 10%): Headache[Ref]


Postmarketing reports: Anaphylactic reactions, anaphylactic shock, anaphylactoid reactions, anaphylaxis, hypersensitivity reactions[Ref]


Postmarketing reports: Angioedema (swelling of face, eyelids, tongue, and lips), rash, urticaria, erythema multiforme[Ref]


Postmarketing reports: Delirium, abnormal behavior, hallucinations

Frequently asked questions


1. "Product Information. Xofluza (baloxavir marboxil)." Genentech, South San Francisco, CA.

2. Cerner Multum, Inc. "Australian Product Information." O 0

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.