What are the side effects of Baloxavir (Baloxavir marboxil)?

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Last updated: April 25, 2025 • View editorial policy

From the Guidelines

Baloxavir is associated with several common side effects, including nausea, vomiting, and diarrhea, as reported in a 2024 study published in Pediatrics 1. The most common adverse events associated with baloxavir are:

  • Nausea
  • Vomiting
  • Diarrhea These side effects are generally mild and temporary. It is essential to note that baloxavir may also interact with certain medications and supplements, which can reduce its effectiveness. According to the study, baloxavir is administered orally, and the dosage varies based on body weight, with a single dose of 2 mg/kg for individuals weighing less than 20 kg, 40 mg for those weighing 20-80 kg, and 80 mg for those weighing more than 80 kg 1. If severe side effects occur, medical attention should be sought immediately. The study also highlights the importance of considering potential interactions with other medications and supplements when prescribing baloxavir 1. Overall, the side effects of baloxavir are generally manageable, and the medication can be an effective treatment option for acute uncomplicated influenza.

From the FDA Drug Label

Table 3 Incidence of Adverse Events Occurring in at Least 1% of Adult and Adolescent Subjects Receiving XOFLUZA in the Acute Uncomplicated Influenza Trials T0821, T0831, and T0832 Adverse Event XOFLUZA(N=1,440) Placebo(N=1,136) Diarrhea 3% 4% Bronchitis 3% 4% Nausea 2% 3% Sinusitis 2% 3% Headache 1% 1%

The most frequently reported AEs (≥ 5%) in all subjects in the XOFLUZA treatment arm were vomiting (5%) and diarrhea (5%).

The following adverse reactions have been identified during postmarketing use of XOFLUZA. Immune System Disorders: Anaphylactic reactions, anaphylactic shock, anaphylactoid reactions, hypersensitivity reactions, angioedema (swelling of face, eyelids, tongue and lips) Skin and Subcutaneous Tissue Disorders: Rash, urticaria, erythema multiforme Gastrointestinal Disorders: Vomiting, hematochezia, melena, colitis Psychiatric Disorders: Delirium, abnormal behavior, hallucinations

The common side effects of Baloxavir include:

  • Diarrhea
  • Bronchitis
  • Nausea
  • Sinusitis
  • Headache
  • Vomiting

The serious side effects of Baloxavir include:

  • Anaphylactic reactions
  • Anaphylactic shock
  • Anaphylactoid reactions
  • Hypersensitivity reactions
  • Angioedema
  • Rash
  • Urticaria
  • Erythema multiforme
  • Hematochezia
  • Melena
  • Colitis
  • Delirium
  • Abnormal behavior
  • Hallucinations [2] [3]

From the Research

Baloxavir Side Effects

  • The most common adverse reactions associated with baloxavir were diarrhea, bronchitis, nausea, nasopharyngitis, and headache 4.
  • Adverse events were reported in 20.7% of baloxavir recipients, 24.6% of placebo recipients, and 24.8% of oseltamivir recipients 5.
  • Baloxavir is well tolerated, with a single oral dose regimen providing a useful alternative to neuraminidase inhibitors for the treatment of acute uncomplicated influenza in adolescents and adults 6.
  • A single oral dose of baloxavir is usually well tolerated; it hastens alleviation of influenza symptoms and shortens the duration of viral shedding 7.
  • No dosage adjustment is needed in patients with mild-to-moderate hepatic or renal impairment 4.

Comparison with Other Antiviral Drugs

  • Baloxavir presents a similar safety and efficacy profile to those of drugs already used in the treatment of influenza 8.
  • The time to alleviation of symptoms was similar with baloxavir and oseltamivir 4, 5.
  • Baloxavir was associated with greater reductions in viral load 1 day after initiation of the regimen than placebo or oseltamivir 5.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.