[Antivirals for influenza]

This paper describes antivirals active against Myxovirus influenzae (influenza vaccine excluded), together with their indications in inter-pandemic and pandemic situations. Three kinds of antiviral drug, with different mechanisms of action, are active against Myxovirus influenzae: the adamantanes (amantadine and rimantadine); ribavirin; and neuraminidase inhibitors (zanamivir and oseltamivir). Amantadine is available in France but its indications are limited by its inactivity against influenza B virus, its adverse effects, and rapid onset of resistance. Ribavirin is administered by nebulization, exclusively in hospital, for severe cases. Neuraminidase inhibitors are effective on benign influenza; they are also well tolerated, active against subtypes A and B, and rarely elicit resistant mutants in vivo (exclusively seen with oseltamivir, mainly among children). According to their licensing terms, antivirals may be prescribed during epidemics, within 24-48 hours of typical symptom onset. They must not be used prophylactically in place of influenza vaccine, but may be useful when there is a familial or institutional index case, or during pandemics. Use in this latter situation would raise supply problems and, thus, the question of who should be treated first.