Xofluza Dosing for Influenza Prophylaxis
For influenza prophylaxis, Xofluza (baloxavir marboxil) is dosed as a single weight-based oral dose: 40 mg for patients weighing 40-80 kg and 80 mg for patients weighing ≥80 kg, approved for individuals ≥12 years of age who weigh >40 kg. 1, 2
Weight-Based Dosing for Prophylaxis
The dosing is identical for both treatment and prophylaxis:
- 40-80 kg body weight: One 40 mg tablet as a single oral dose 1, 2
- ≥80 kg body weight: One 80 mg tablet as a single oral dose 1, 2
Age and Weight Restrictions
- Approved only for patients ≥12 years of age who weigh more than 40 kg 1
- Patients weighing <40 kg are not included in the approved prophylaxis indication 1
Timing and Administration
- Administer as soon as possible following contact with an individual who has influenza 2
- Given as a single dose (not a multi-day regimen like oseltamivir) 1, 2
- May be taken with or without food 2
Critical Administration Precautions
Avoid coadministration with dairy products, calcium-fortified beverages, polyvalent cation-containing laxatives, antacids, or oral supplements (calcium, iron, magnesium, selenium, zinc) as these significantly reduce baloxavir absorption 2
Alternative Formulation for Prophylaxis
For patients ≥5 years who cannot swallow tablets, Xofluza oral suspension is available:
- <20 kg: 2 mg/kg as a single dose 2
- 20 kg to <80 kg: 40 mg (20 mL) as a single dose 2
- ≥80 kg: 80 mg (40 mL, requires two bottles) as a single dose 2
The oral suspension must be constituted by a healthcare provider and administered within 10 hours of constitution 2
Comparison to Treatment Dosing
The prophylaxis dosing is identical to the treatment dosing regimen—both use the same single weight-based dose 1, 2. This differs from oseltamivir, where prophylaxis uses once-daily dosing versus twice-daily for treatment 1
Important Clinical Context
While the 2019 AAP guidelines listed baloxavir prophylaxis as "not recommended" 1, the FDA subsequently approved baloxavir for post-exposure prophylaxis 2, and the most recent 2021-2022 AAP guidelines include prophylaxis dosing in their recommendations 1. The 2024-2025 AAP guidelines confirm this indication continues 1.