Clinical efficacy and safety of the orally inhaled neuraminidase inhibitor zanamivir in the treatment of influenza: a randomized, double-blind, placebo-controlled European study

Abstract

Objectives: To assess the clinical efficacy and safety of orally inhaled zanamivir in the treatment of influenza in a European primary care setting.

Methods: This was a randomized, double-blind, placebo-controlled trial in primary care and hospital clinics in 11 European countries. Patients aged > or = 12 years were recruited within 2 days of onset of typical influenza symptoms and received orally inhaled zanamivir 10 mg via a Diskhaler twice daily for 5 days or matching placebo. Influenza symptoms and temperature were recorded daily for 14 days. The primary endpoint was time to alleviation of clinically significant symptoms of influenza. Other endpoints included symptom severity, use of relief medications, time to return to normal activities, complications and investigator's assessment of symptoms.

Results: A total of 356 patients were recruited; 277 (78%) had laboratory-confirmed influenza and 32 (9%) were considered high-risk (i.e. elderly or with underlying medical conditions). Zanamivir significantly reduced the time to alleviation of symptoms versus placebo (median 5 days versus 7.5 days, P<0.001), a 33% reduction in duration of illness. Zanamivir significantly reduced the severity of several symptoms; improvements versus placebo were discernible after approximately 24 h. The proportion of patients who were afebrile after 24 h increased by 46% versus placebo. Similar treatment benefits were observed in the high-risk patients. Zanamivir was well tolerated, with an adverse event profile similar to that of placebo.

Conclusions: Zanamivir is effective in reducing the duration and severity of influenza illness and is well tolerated. Zanamivir should therefore be a clinically valuable intervention in the management of influenza.