Xofluza Dosing for an 81kg Patient
For an 81kg patient, administer a single 80mg oral dose of Xofluza (baloxavir marboxil). 1
Weight-Based Dosing Algorithm
The FDA-approved dosing for Xofluza follows a clear weight-based threshold 1:
- Patients weighing ≥80 kg: Single 80mg dose (one 80mg tablet) 1
- Patients weighing 20 kg to <80 kg: Single 40mg dose (one 40mg tablet) 1
Since your patient weighs 81kg, they cross the 80kg threshold and require the higher 80mg dose. 1
Administration Timing and Guidelines
- Administer as soon as possible within 48 hours of influenza symptom onset for treatment or following contact with an influenza-infected individual for post-exposure prophylaxis 1
- Single dose only - no repeat dosing required 1
- May be taken with or without food 1
Critical Administration Precautions
Avoid coadministration with the following, as they significantly reduce baloxavir absorption 1:
- Dairy products 1
- Calcium-fortified beverages 1
- Polyvalent cation-containing laxatives 1
- Antacids 1
- Oral supplements containing calcium, iron, magnesium, selenium, or zinc 1
Dosing Consistency Across Indications
The American Academy of Pediatrics confirms that prophylaxis dosing is identical to treatment dosing - the same single 80mg dose applies whether treating active influenza or providing post-exposure prophylaxis in this weight category. 2, 3
Clinical Efficacy Context
High-quality evidence demonstrates that baloxavir 80mg in patients ≥80kg reduces time to symptom improvement by approximately 29 hours compared to placebo (median 73.2 vs 102.3 hours, p<0.0001), with efficacy similar to oseltamivir but with superior viral load reduction. 4 The single-dose regimen offers a significant adherence advantage over the 5-day twice-daily oseltamivir course. 4, 5, 6
Resistance Monitoring Caveat
Be aware that polymerase acidic protein variants with reduced baloxavir susceptibility emerged in approximately 5-10% of treated patients in clinical trials, particularly with influenza A(H3N2). 4, 7 However, this does not alter the initial dosing recommendation, though it underscores the importance of clinical follow-up if symptoms fail to improve. 4