Comparison of efficacy and safety of oseltamivir and zanamivir in pandemic influenza treatment

Aim: In 2009, a flu pandemic caused panic worldwide. Oseltamivir and zanamivir were widely used in this pandemic. Currently, there are a limited number of studies comparing the efficacy and tolerability of these two drugs. This study aimed to compare the efficacy and tolerability of these two drugs in the treatment of influenza. Materials and Methods: Patients diagnosed with influenza at our infectious disease outpatient clinic during the influenza season between October 1, 2009 and February 1, 2010 were included in the study. Study data were obtained retrospectively from files for consecutive patients. A total of 136 subjects were selected. After exclusion criteria were applied, 56 subjects were discarded. The information for 80 patients in whom oseltamivir or zanamivir therapy was initiated (40 for each therapy) was compiled, and the efficacy and tolerability of the drugs were compared. Results: There was no significant difference in efficacy for the two drugs (P > 0.05). Temperature normalization was significantly faster in patients taking zanamivir (P = 0.0157). Drowsiness was the most frequent adverse event for both drugs (38 for the oseltamivir group, and 22 for the zanamivir group). Respiratory distress was observed in five patients in the zanamivir group, whereas it was not observed in patients in the oseltamivir group (P < 0.05). One patient had to discontinue therapy in the zanamivir group due to respiratory distress. Conclusion: Efficacy (in terms of symptom relief and duration to resumption of work) and adverse events were similar for zanamivir and oseltamivir, but temperature normalization was much more rapid in patients using zanamivir. Patients using zanamivir should be monitored for respiratory distress.