Efficacy and safety of inhaled zanamivir for the treatment of influenza in patients with asthma or chronic obstructive pulmonary disease -: A double-blind, randomised, placebo-controlled, multicentre study

Background: Influenza in patients with asthma can cause acute exacerbation and in patients with chronic obstructive pulmonary disease (COPD) it can lead to respiratory distress. Zanamivir is an effective treatment for both influenza A and B. However, controlled studies with zanamivir specifically in asthma or COPD patients with influenza illness are limited. Objective: To investigate the clinical efficacy and safety of inhaled zanamivir for the treatment of influenza in patients with asthma or COPD. Design and Setting: This randomised, double-blind, placebo-controlled, multicentre study was conducted at 159 sites in 15 countries. Patients and Participants: 525 patients with asthma or COPD aged greater than or equal to 12 years and with influenza-like illness were enrolled; 313 (60%) of these had laboratory-confirmed influenza virus infection and were included in the primary efficacy analysis. Methods: Patients were randomised to inhaled zanamivir 10mg or matching placebo via Diskhaler(TM) twice daily for 5 days. Patients recorded symptoms and pulmonary function twice daily in diary cards. The primary end-point in both patient groups was time to alleviation of symptoms of influenza. Results: Zanamivir significantly reduced the median time to alleviation of influenza symptoms compared with placebo (5.5 days vs 7.0 days; difference 1.5 days; 95% confidence interval 0.50 to 3.25 days; p = 0.009). Zanamivir significantly reduced the mean overall influenza assessment score compared with placebo (p = 0.004) over days 1 to 5. Patients recorded fewer nights of sleep disturbance with zanamivir compared with placebo (median 2 nights vs 3 nights; p = 0.042) during treatment. Zanamivir reduced the incidence of complications (requiring antibiotics and a change in respiratory medication) compared with placebo by 58% (p = 0.064). Zanamivir did not adversely affect pulmonary function, as determined by measurements of forced expiratory volume in 1 second and peak expiratory flow rate, compared with placebo. Zanamivir was well tolerated, with a safety profile similar to placebo. Compliance with treatment was high, with 495 (94%) patients successfully completing at least 4 days of treatment (8 doses). Furthermore, 90% of patients felt that the Diskhaler(TM) was easy or very easy to use. Conclusion: Zanamivir is an effective treatment for influenza in patients with asthma or COPD, and has a safety profile similar to that of placebo. Importantly, zanamivir does not adversely affect pulmonary function in this high-risk population.