Although the sooner NAIs are initiated the more likely the odds of a favorable impact on the course of influenza, the FDA approval of these drugs was based on study in relatively healthy ambulatory patients not those who require hospitalization and are generally much sicker. There are no randomized studies but several observational studies support the benefit of NAIs even when initiated after 48 h of onset of the disease. One study reported improvement in survival even when treatment was delayed for 4-5 days after symptom onset (1), while others have reported more rapid viral clearance and clinical benefit in severe infections even when antivirals were initiated after 48 h (2).
Collectively , these data suggest that in the presence of ongoing symptoms and likely active viral replication, NAI treatment should be seriously considered in hospitalized patients who are likely to have more severe disease. CDC recommends “initiation of antiviral treatment as early as possible” in hospitalized patients, and states that “antiviral treatment might be effective in reducing morbidity and mortality in hospitalized patients even if treatment is not started until >48 hours after onset of illness.” (3)
- Louie JK, Yang S, Acosta M, et al. Treatment with neuraminidase inhibitors for critically ill patients with influenza A (H1N1) pdm09. Clin Infect Dis 2012;44:1198-1204.
- Lee N, Ison MG. “Late” treatment with neuraminidase inhibitors for severely ill patients with influenza: better late than never?
- CDC. Antiviral agents for the treatment and chemoprophylaxis of influenza: recommendations of the Advisory Committee on Immunization Practices. MMWR 2011;60 (RR01):1-24.