How does delayed influenza treatment affect the efficacy of antiviral drugs?

Updated: Aug 07, 2020
  • Author: Hien H Nguyen, MD, MS; Chief Editor: Michael Stuart Bronze, MD  more...
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Prompt use of antiviral drugs during the 2009 H1N1 influenza pandemic improved survival among severely ill pregnant women. A CDC study of 347 pregnant women (including 272 who required ICU admission but survived and 75 who died) and 15 severely ill postpartum women (9 of whom died) found that 94.8% of survivors received antiviral treatment with oseltamivir or zanamivir, compared with 86.1% of those who died, a statistically significant difference. [55]

Time from symptom onset to initiation of treatment was significantly longer for women who died than for those who survived. Only 7% of those who died received an antiviral within 2 days of symptom onset, compared with 41% of survivors. This analysis reaffirms the importance of prevention (ie, vaccination of pregnant women regardless of trimester) and prompt treatment with a neuraminidase inhibitor (ie, within 2 days of symptom onset) if influenza occurs during pregnancy. [55]

A meta-analysis of outcome in patients hospitalized with H1N1 influenza during the 2009-2010 pandemic found that early treatment with neuraminidase inhibitors (ie, within 48 hours of symptom onset) reduced the death rate by 63%. Although neuraminidase treatment (early or late) during hospitalization did not produce a statistically significant reduction in severe outcomes (eg, critical care unit admission), preadmission use did. [78]

Lam et al suggested that cases of suspected severe influenza infection should be treated early and aggressively, even before diagnostic tests can be confirmed. [79] In their study, a higher dose of oseltamivir and nonconventional methods of ventilation improved outcome in patients with pandemic H1N1 2009 infection.

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