Xofluza (Baloxavir Marboxil) Dosing
Xofluza is dosed as a single weight-based oral dose: 40 mg for patients weighing 20 to <80 kg, and 80 mg for patients weighing ≥80 kg, taken within 48 hours of symptom onset for treatment or following exposure for prophylaxis. 1
Weight-Based Dosing for Patients ≥5 Years
Tablet Formulation
Oral Suspension Formulation
- <20 kg: 2 mg/kg as a single dose 1
- 20 kg to <80 kg: 40 mg (20 mL) as a single dose 1
- ≥80 kg: 80 mg (40 mL) as a single dose 1
Age Restrictions and Indications
Xofluza is approved for patients ≥5 years of age only. 1
- Treatment indication: Acute uncomplicated influenza in patients ≥5 years who have been symptomatic for ≤48 hours 1
- Prophylaxis indication: Post-exposure prophylaxis in patients ≥5 years following contact with an individual who has influenza 1, 2
- Not indicated in children <5 years: Higher incidence of treatment-emergent resistance observed in this age group 1
Timing of Administration
Administer as soon as possible within 48 hours of symptom onset for treatment or following exposure for prophylaxis. 1 The same single-dose regimen applies to both treatment and prophylaxis. 2
Renal Function Considerations
No dose adjustment is required based on renal function. 1 This represents a significant advantage over oseltamivir, which requires dose reduction when creatinine clearance is 10-30 mL/min. 3
Administration Instructions
Food Interactions
- May be taken with or without food 1
Critical Drug Interactions to Avoid
Do not coadminister with dairy products, calcium-fortified beverages, or polyvalent cation-containing products (laxatives, antacids, or oral supplements containing calcium, iron, magnesium, selenium, or zinc). 1, 4 These products significantly reduce baloxavir absorption and antiviral efficacy. 4
Live Attenuated Influenza Vaccine Interaction
Live attenuated influenza vaccines may be affected by antivirals. 1 Avoid administering live attenuated influenza vaccine within 2 weeks before or 48 hours after Xofluza administration, similar to other antivirals. 3
Clinical Efficacy Data
In high-risk patients weighing ≥80 kg, the 80 mg dose reduces time to symptom improvement by approximately 29 hours compared to placebo (median 73.2 hours vs 102.3 hours). 5, 6 Baloxavir demonstrates superior viral load reduction compared to oseltamivir at 24 hours post-dose. 5, 7
Safety Profile
Adverse events are mild and comparable to placebo, occurring in approximately 20-25% of patients. 5, 7 The most common adverse events include diarrhea, bronchitis, nausea, and headache. 1, 8
Important Caveats
Resistance Emergence
Treatment-emergent polymerase acidic protein variants with reduced baloxavir susceptibility (I38T/M/F substitutions) emerged in approximately 2-10% of treated patients in clinical trials. 5, 7 This is higher than the resistance rates seen with neuraminidase inhibitors, though clinical significance remains under investigation. 9
Contraindications
Contraindicated in patients with hypersensitivity to baloxavir marboxil or any ingredient. 1 Hypersensitivity reactions including anaphylaxis, angioedema, urticaria, and erythema multiforme have been reported. 1
Bacterial Superinfection Risk
Xofluza does not prevent secondary bacterial infections, which may begin with influenza-like symptoms or occur as complications. 1 Maintain vigilance for bacterial superinfection and treat appropriately.