Safety and efficacy of the neuraminidase inhibitor zanamivir in treating influenza virus infection in adults: results from Japan

The study was carried out to evaluate the therapeutic effects of zanamivir, a highly selective, potent and specific inhibitor of influenza A and B vir us neuraminidases, in adult patients with acute influenzalike illness. Pati ents who presented within 36 h of the onset of influenza-like symptoms were randomly assigned to receive one of three treatments, twice daily, for 5 d ays: 10 mg zanamivir powder for inhalation (zanamivir inhalation group), 10 mg zanamivir powder for inhalation plus 6.4 mg zanamivir nasal spray (zana mivir inhalation plus intranasal group) or placebo (placebo group). The pri mary end point was the time to alleviation of the three major symptoms (fev er, headache and myalgia). The secondary end point was the time to alleviat ion of five influenza symptoms (fever, headache, myalgia, cough and sore th roat). One hundred and sixteen patients with influenza-like illness were re cruited to the study. No differences were observed between the two groups o f patients who received zanamivir (inhalation group or inhalation plus intr anasal group). Patients who received zanamivir recovered significantly fast er (median 3 days to recovery) than the patients in the placebo group (medi an 4 days to recovery; P < 0.01). Topically administered zanamivir was well tolerated. This study confirms that in adults, topically administered zana mivir is well tolerated and is effective in reducing the time to alleviatio n of influenza symptoms.