Influenza Treatment with Zanamivir
Choices for influenza management in the United States to date include prophylaxis by vaccination or the antiviral medications amantadine and rimantadine. Treatment with either antiviral within 48 hours of onset of influenza A virus has been shown to be effective. Unfortunately, influenza B virus is unaffected by these antivirals, and resistant viral strains do emerge associated with antiviral therapy.
The current trial investigated the use of zanamivir, an analogue of sialic acid. Zanamivir inhibits influenza virus neuraminidase, preventing replication of either influenza A or influenza B virus. In laboratory situations, treatment within 24 hours of influenzavirus challenge dramatically reduced peak viral titers and frequency of febrile illness. This report details the response of naturally occurring acute influenza in the community to nasal and pulmonary inhalation of zanamivir.
Use of zanamivir was associated with a 20% decrease in days of illness for all major influenza symptoms. Influenza-infected patients treated at the earliest stages of disease (< 30 hours duration) averaged four days sick, compared with seven days in the placebo group. Active drug was also associated with a 33% reduction in duration of viral shedding, decreasing the likelihood of spread to others. Although side effects were reported, many were typical of the actual underlying disease process, hence difficult to attribute to the drug. From this study, it appears that zanamivir may be a useful addition to the influenza management armamentarium.
Hayden FG, et al. N Engl J Med 1997; 337:874-880.
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