Baloxavir marboxil

Administration

• Type: Antiviral
• Dosage Forms:
  • 20 mg, 40 mg tab
  • reconstituted solution 2 mg/mL
  • 30 mg, 40 mg packets for reconstitution
• Routes of Administration: PO
• Common Trade Names: Xofluza

Indications

• Influenza

Adult Dosing

• 40-79.9 kg: 40 mg PO x1
  • Start within 48 hours of symptom onset
  • Avoid co-administration with dairy products, calcium supplements
• >80 mg: 80 mg PO x1
  • Start within 48 hours of symptom onset
  • Avoid co-administration with dairy products, calcium supplements

Pediatric Dosing

As of 2025, FDA-approved for acute uncomplicated influenza in patients 5 years of age and older who have been symptomatic for no more than 48 hours and who are otherwise healthy or at high risk of developing influenza-related complications, and, post-exposure prophylaxis of influenza in patients 5 years of age and older following contact with an individual who has influenza.

• Oral bottle suspension:
  • Less than 20kg: 2mg/kg PO x1
  • 20kg to <80kg: 40 mg (20 mL)
  • 80kg and up: 80 mg (40 mL)
• Oral packet suspension:
  • 15kg to <20kg: 30mg oral packet (suspension) PO x1
  • 20kg to <80kg: 40mg oral packet (suspension) PO x1
  • 80kg and up: 80 mg (two 40 mg packets) PO x1
• Oral tablet:
  • 40kg to <80kg: 40 mg PO x1
  • 80 kg and up: 80 mg PO x1
• Notes:
  • Start within 48 hours of symptom onset
  • Avoid co-administration with dairy products, calcium supplements

Special Populations

• Pregnancy Category: Not assigned (insufficient data)
• Lactation risk: Avoid use while breastfeeding

Renal Dosing

• Adult and Pediatric:
  • CrCl>50: no adjustment
  • CrCl<50 or HD/PD: not defined

Hepatic Dosing

• Adult and Pediatric:
  • Child-Pugh Class A or B: no adjustment
  • Child-Pugh Class C: not defined

Contraindications

• Allergy to class/drug
• Pregnancy
• Breastfeeding

Adverse Reactions

Serious

• Anaphylaxis
• Angioedema
• Erythema multiforme
• Urticaria

Common

• Nausea (Especially in older patients)

Pharmacology

• Half-life: 79.1 hours
• Metabolism: liver (CYP450)
• Excretion: Feces (predominant), urine

Mechanism of Action

• Inhibits viral polymerase acidic protein endonuclease activity, which inhibits viral replications

Comments

• More expensive but one time dosing. Only approved for patients 5 years old and older, no current safety data exists for pregnancy and breastfeeding. The effect of severe renal or hepatic impairment on baloxavir pharmacokinetics has not been evaluated.
• The trial reported a 29.1-hour advantage over placebo (73.2h vs 102.3h), but this represents only a 28% relative improvement in a soft endpoint. The more clinically relevant metric, time to return to pre-illness health, showed no significant difference (126.4h vs 149.8h, p=0.46)

See Also

• Influenza
• Antiviral
• Tamiflu/Oseltamivir