FDA Expands Indication of Antiviral Therapy to Include Post-Exposure Influenza Prevention

Originally approved in 2018, baloxavir marboxil is indicated for patients aged 12 years and older.

Officials with the FDA expanded the approved indication for baloxavir marboxil (Xofluza; Genentech) to include post-exposure prevention of influenza for patients aged 12 years and older, after contact with an individual who has the flu. The therapy previously available only in tablet form, is also now available as granules for mixing in water.

Baloxavir marboxil was originally approved in 2018 for treating uncomplicated flu in patients aged 12 years and older who have been symptomatic for no more than 48 hours. Its’ indication was first expanded in 2019 for patients aged 12 years and older who are at high risk for developing influenza-associated complications.

Baloxavir marboxil’s safety and efficacy for post-flu exposure prevention is supported by a randomized, double-blind, controlled trial in which 607 subjects, aged 12 years and older who were exposed to a person with influenza in their household, received either a single dose of baloxavir marboxil or a single dose of a placebo. Of these 607 subjects, 303 received baloxavir marboxil and 304 received the placebo.

According to the FDA, the trial’s primary endpoint was the proportion of subjects who were infected with influenza virus and presented with fever and at least 1 respiratory symptom from day 1 to day 10. Of those who received baloxavir marboxil, 1% of subjects met these criteria, compared to 13% of subjects who received a placebo for the clinical trial.

The most common adverse effects of baloxavir marboxil include diarrhea, bronchitis, nausea, sinusitis and headache. Additionally, hypersensitivity, including anaphylaxis, can occur in patients taking baloxavir marboxil.

Patients should be advised not be co-administer baloxavir marboxil with dairy products, calcium-fortified beverages, or laxatives, antacids, or oral supplements containing calcium, iron, magnesium, selenium, aluminum or zinc.

Flu is a contagious respiratory illness caused by influenza viruses. According to the FDA, treating flu patients with antiviral drugs within 48 hours of their becoming sick can reduce symptoms and duration of the illness. An annual seasonal flu vaccine is the best way to protect against the flu.


FDA Expands Approval of Influenza Treatment to Post-Exposure Prevention [news release]. Silver Spring, MD; November 23, 2020: FDA. Accessed November 23, 2020. https://www.fda.gov/news-events/press-announcements/fda-expands-approval-influenza-treatment-post-exposure-prevention

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