Main outcome measures Time to alleviation of clinical symptoms, which had to be maintained for 24 hours. Secondary outcomes were mean symptom score, sleep disturbance, time to return to normal activities, and use of acetaminophen and dextromethorphan to relieve symptoms. Main results Analysis was by intention to treat. Zanamivir was superior to placebo in all secondary clinical outcomes. The groups did not differ for adverse events.
Influenza remains a major cause of morbidity and mortality each year.
Although vaccination is the primary method for preventing influenza, antiviral agents play an important complementary role for preventing and treating the disease. Before 1999, amantadine and rimantadine were the only antiviral agents available and were active only against influenza A viruses. The neuraminidase inhibitors appear to be much less likely to induce resistance. Zanamivir and oseltamivir are effective for the treatment of in-fluenza A or B among adults when started within 2 days of onset of symptoms. Monto and colleagues administered zanamivir by nasal spray and in its currently available form of orally inhaled powder.