Table 1.

Overview of influenza antivirals used in the 2009 pandemic and those now licensed and available for use in future pandemics.

Antiviral (Trade Name)	Mode of Action	Use in the 2009 Pandemic	Potential Use in a Future Pandemic
Amantadine/rimantadine (Symmetrel/Flumadine)	M2 ion channel inhibitor	Limited/no use due to the 2009 pandemic virus being adamantane-resistant at the time of emergence	Unlikely to be used in a future pandemic due to rapid selection of resistance
Oseltamivir (Tamiflu)	Neuraminidase inhibitor	Major component of WHO and country stockpiles	Likely to remain a part of future stockpiles due to long “shelf-life”, ease of oral delivery and familiarity with its use for seasonal influenza
Zanamivir (Relenza)	Neuraminidase inhibitor	Minor component of WHO and some country stockpiles	Likely to make up only a minor component or not be used due to inhaled delivery and low use for seasonal influenza. Has a low propensity to select for resistance, which is a benefit
Peramivir (Rapivab)	Neuraminidase inhibitor	Some use in Japan where it was licensed. Small usage elsewhere under emergency use authorisation only	May be utilised in small quantities given it is approved for intravenous delivery, which may be optimal for some severely ill patients
Laninamivir (Inavir)	Neuraminidase inhibitor	Was not available	May be used in Japan (the only country to license the antiviral for seasonal influenza use). Has benefits of single dose and low propensity to select for resistance, but is delivered via inhalation
Favipiravir (Avigan)	Polymerase inhibitor (purine nucleoside altering role of PB1)	Was not available	Limited use due to concerns of teratogenicity. May be used in Japan if pandemic virus is resistant to other available antivirals. Unlikely to be used elsewhere
Baloxavir (Xofluza)	Polymerase inhibitor (PA endonuclease)	Was not available	Likely to be a part of future stockpiles due to ease of dosing and delivery (single oral dose) and rapid virological effect