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Baloxavir Marboxil

Medically reviewed by Last updated on Jun 24, 2019.


(ba LOX A veer mar BOX el)

Index Terms

  • S-033188
  • Xofluza

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet Therapy Pack, Oral:

Xofluza: 2 x 20 MG (2 ea); 2 x 40 MG (2 ea)

Brand Names: U.S.

  • Xofluza

Pharmacologic Category

  • Antiviral Agent
  • Endonuclease Inhibitor


Baloxavir marboxil is an oral prodrug that is converted to baloxavir, an inhibitor of the endonuclease activity of a selective polymerase acidic (PA) protein, which is required for viral gene transcription, resulting in inhibition of influenza virus replication. Baloxavir has demonstrated antiviral activity against influenza A and B viruses, including strains resistant to standard current antiviral agents (Hayden 2018).


Vd: 1,180 L


Baloxavir marboxil is a prodrug; completely converted via UGT1A3 (major) and CYP3A4 (minor) to the active metabolite (baloxavir)


Feces (80.1%); Urine (14.7%; 3.3% as baloxavir)

Time to Peak

4 hours

Half-Life Elimination

79.1 hour

Protein Binding

~93% to 94%

Special Populations Note

Body weight: As weight increases, exposure to baloxavir decreases.

Use: Labeled Indications

Influenza, treatment: Treatment of acute uncomplicated influenza in patients ≥12 years who have been symptomatic for no more than 48 hours.

Limitations of use: Influenza viruses change over time, and factors such as the virus type or subtype, emergence of resistance, or changes in viral virulence may diminish the clinical benefit of antiviral drugs. Consider available information on drug susceptibility patterns for circulating influenza virus strains when deciding whether to use baloxavir marboxil.


Hypersensitivity to baloxavir marboxil or any component of the formulation

Dosing: Adult

Influenza, treatment: Oral:

40 to <80 kg: 40 mg as a single dose within 48 hours of onset of influenza symptoms

≥80 kg: 80 mg as a single dose within 48 hours of onset of influenza symptoms

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Influenza, treatment: Note: Treatment should ideally begin within 48 hours of symptom onset. Children ≥12 years and Adolescents: Oral:

40 to <80 kg: 40 mg once as a single dose

≥80 kg: 80 mg once as a single dose


Oral: Initiate within 48 hours of influenza symptom onset. Administer a single dose with or without food. Avoid administration with dairy products, calcium-fortified beverages, polyvalent cation-containing laxatives, antacids, or oral supplements (eg, calcium, iron, magnesium, selenium, zinc).


Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F). Store in original blister package.

Drug Interactions

Influenza Virus Vaccine (Live/Attenuated): Antiviral Agents (Influenza A and B) may diminish the therapeutic effect of Influenza Virus Vaccine (Live/Attenuated). Management: Avoid anti-influenza antivirals during the period beginning 48 hours prior to and ending 2 weeks after live influenza virus vaccine administration. Consider therapy modification

Polyvalent Cation Containing Products: May decrease the serum concentration of Baloxavir Marboxil. Avoid combination

Adverse Reactions

1% to 10%:

Gastrointestinal: Diarrhea (2%; Hayden 2018)

Respiratory: Nasopharyngitis (2%; Hayden 2018)


Concerns related to adverse effects:

• Bacterial infection: There is no evidence of efficacy of baloxavir marboxil in illnesses (eg, bacterial infections) caused by pathogens other than influenza viruses. Serious bacterial infections may begin with influenza-like symptoms, may coexist with, or occur as an influenza complication. Baloxavir marboxil has not been shown to prevent such complications. Monitor for potential secondary bacterial infections and manage appropriately.

Concurrent drug therapy issues:

• Drug-drug/drug-food interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Monitoring Parameters

Monitor for potential secondary bacterial infections.

Pregnancy Considerations

Adverse events were not observed in animal reproduction studies.

Untreated influenza infection is associated with an increased risk of adverse events to the fetus and an increased risk of complications or death to the mother. Other agents are currently recommended for the treatment of influenza in pregnant females and females up to 2 weeks postpartum (ACOG 2018; CDC [Fiore] 2011).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience diarrhea, common cold symptoms, rhinitis, pharyngitis, cough, headache, or nausea (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

Further information

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

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