Xofluza (baloxavir marboxil) Side Effects, Warnings, and Drug Interactions

Xofluza (baloxavir marboxil) is an antiviral drug used to treat acute uncomplicated influenza, or the common flu, in patients 12 years of age and older who have been symptomatic for no more than 48 hours. 

Influenza viruses change over time, and factors such as the virus type or subtype, emergence of resistance, or changes in viral virulence could diminish the clinical benefit of antiviral drugs. 

Consider available information on drug susceptibility patterns for circulating influenza virus strains when deciding whether to use Xofluza. Xofluza is not effective in treating infections other than influenza. Other kinds of infections can appear like flu or occur along with flu and may need different kinds of treatment.

Common side effects of Xofluza include:

• diarrhea,
• bronchitis,
• common cold symptoms,
• headache, and
• nausea.

Serious side effects of Xofluza include:

• allergic reactions. Symptoms of allergic reactions may include trouble breathing, skin rash, hives or blisters, swelling of the face/throat/mouth, and dizziness or lightheadedness.

Drug interactions of Xofluza include polyvalent cation-containing products such as laxatives, antacids, or oral supplements (e.g., calcium, iron, magnesium, selenium, or zinc), which may reduce Xofluza efficacy. 

Use of Xofluza with intranasal live attenuated influenza vaccine (LAIV) has not been evaluated. Concurrent administration of antiviral drugs may inhibit viral replication of LAIV and thereby decrease the effectiveness of LAIV vaccination. 

There are no available data on Xofluza use in pregnant women to inform a drug-associated risk of adverse developmental outcomes. There are risks to the mother and fetus associated with influenza virus infection in pregnancy. 

There are no data on the presence of Xofluza in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for Xofluza and any potential adverse effects on the breastfed child from the drug or from the underlying maternal condition.

The most common side effects of Xofluza in adults and adolescents include:

• diarrhea
• bronchitis
• common cold symptoms (nasopharyngitis)
• headache
• nausea

Xofluza is not effective in treating infections other than influenza. Other kinds of infections can appear like flu or occur along with flu and may need different kinds of treatment. Tell your healthcare provider if you feel worse or develop new symptoms during or after treatment with Xofluza or if your flu symptoms do not start to get better.

These are not all the possible side effects of Xofluza. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800 FDA-1088.

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety profile of Xofluza is based on data from 3 placebo-controlled trials in which a total of 1,640 subjects received Xofluza:

• 1,334 subjects (81%) were 18 to 64 years of age,
• 209 subjects (13%) were adults 65 years of age or older and
• 97 subjects (6%) were adolescents 12 to 17 years of age.

These trials included otherwise healthy adults and adolescents (N=910) and subjects at high risk of developing complications associated with influenza (N=730). Of these, 1,440 subjects received Xofluza at the recommended dose.

Table 2 displays the most common adverse events (regardless of causality assessment) reported in at least 1% of adult and adolescent subjects who received Xofluza at the recommended dose in Trials 1, 2 and 3.

Table 2: Incidence of Adverse Events Occurring in At Least 1% of Subjects Receiving Xofluza in the Acute Uncomplicated Influenza Trials 1, 2, and 3

Postmarketing Experience

The following adverse reactions have been identified during postmarketing use of Xofluza. Because these reactions are reported voluntarily from a population of uncertain size, it is not possible to reliably estimate their frequency or establish a causal relationship to Xofluza exposure.

Body as a Whole: Swelling of the face, eyelids or tongue, dysphonia, angioedema, anaphylactic reactions, anaphylactic shock, anaphylactoid reactions

Skin and Subcutaneous Tissue Disorders: Rash, urticaria, erythema multiforme

Gastrointestinal disorders: Vomiting, bloody diarrhea, melena, colitis

Psychiatric: Delirium, abnormal behavior, and hallucinations

Effect Of Other Drugs On Xofluza

Co-administration with polyvalent cation-containing products may decrease plasma concentrations of baloxavir which may reduce Xofluza efficacy. Avoid co-administration of Xofluza with polyvalent cation-containing laxatives, antacids, or oral supplements (e.g., calcium, iron, magnesium, selenium, or zinc).

Vaccines

The concurrent use of Xofluza with intranasal live attenuated influenza vaccine (LAIV) has not been evaluated. Concurrent administration of antiviral drugs may inhibit viral replication of LAIV and thereby decrease the effectiveness of LAIV vaccination. Interactions between inactivated influenza vaccines and Xofluza have not been evaluated.