Xofluza (Baloxavir Marboxil) Dosing
Xofluza is dosed as a single oral dose based on body weight: 2 mg/kg for patients <20 kg, 40 mg for 20-80 kg, and 80 mg for ≥80 kg, administered within 48 hours of symptom onset for treatment or after exposure for prophylaxis. 1
Approved Indications
Xofluza is FDA-approved for:
- Treatment of acute uncomplicated influenza in patients ≥5 years old
- Post-exposure prophylaxis in patients ≥5 years old following contact with an influenza case 1
Weight-Based Dosing
For Patients ≥5 Years Old
Single oral dose (treatment or prophylaxis):
- <20 kg: 2 mg/kg
- 20 kg to <80 kg: 40 mg (one tablet or packet)
- ≥80 kg: 80 mg (one 80 mg tablet or two 40 mg packets) 1
Formulations Available
- Tablets: 40 mg and 80 mg
- Oral suspension packets: 30 mg and 40 mg
- Oral suspension bottles: 2 mg/mL concentration (for patients <15 kg or those unable to swallow tablets) 1
Administration Guidelines
Timing
- Administer within 48 hours of symptom onset for treatment
- Administer within 48 hours of exposure for prophylaxis 1
Food and Drug Interactions
Critical: Avoid concomitant administration with:
- Dairy products
- Calcium-fortified beverages
- Polyvalent cation-containing laxatives or antacids
- Oral supplements containing calcium, iron, magnesium, selenium, or zinc
These products significantly reduce baloxavir absorption and antiviral efficacy 1, 2
Xofluza may be taken with or without food otherwise 1
Contraindications
Absolute contraindication: History of hypersensitivity to baloxavir marboxil or any ingredient, including:
- Anaphylaxis
- Angioedema
- Urticaria
- Erythema multiforme 1
Special Populations and Warnings
NOT Indicated for Children <5 Years
Xofluza is contraindicated in children <5 years old due to significantly higher treatment-emergent resistance rates (40% in children <5 years vs. 16% in ages 5-12 years vs. 7% in ≥12 years) 1
Immunocompromised Patients
Not recommended as monotherapy in severely immunocompromised patients due to resistance concerns 3
Pregnancy and Breastfeeding
Not recommended for pregnant or breastfeeding women 3
Renal Impairment
No dose adjustment needed for mild-to-moderate renal impairment 4
Hepatic Impairment
No dose adjustment needed for mild-to-moderate hepatic impairment 4
Clinical Context from Guidelines
The most recent AAP guidelines (2024-2025) include baloxavir in their antiviral recommendations but note specific limitations 3:
- Duration: Single dose (vs. 5 days for oseltamivir)
- Common adverse events: Nausea, vomiting, diarrhea 3
- Not recommended for chemoprophylaxis in institutional outbreak settings where oseltamivir is preferred 3
Key Clinical Advantages
- Single-dose regimen eliminates adherence concerns 5, 6
- Novel mechanism (cap-dependent endonuclease inhibitor) provides alternative for neuraminidase inhibitor-resistant viruses 5, 6
- Rapid viral load reduction within 24 hours, superior to oseltamivir 5, 7
Important Caveats
- Limited data in hospitalized patients, high-risk populations, and combination therapy 6
- Resistance can develop after single dose, particularly in younger children 1, 6
- No evidence for efficacy in bacterial co-infections or complications 1
- Oral suspension (bottles) must be used within 10 hours of reconstitution 1