A comparison of the effectiveness of zanamivir and oseltamivir for the treatment of influenza A and B.

Author(s): Kawai N, Ikematsu H, Iwaki N, Maeda T, Kanazawa H, Kawashima T, Tanaka O, Yamauchi S, Kawamura K, Nagai T, Horii S, Hirotsu N, Kashiwagi S

Affiliation(s): Japan Physicians Association, Tokyo Medical Association Building 3F, 2-5 Kanda-Surugadai, Chiyoda-ku, 101-0062 Tokyo, Japan. nkawai@city.gifu.med.or.jp

Publication date & source: 2008-01, J Infect., 56(1):51-7. Epub 2007 Oct 15.

Publication type: Clinical Trial; Comparative Study; Multicenter Study; Randomized Controlled Trial

OBJECTIVE: To compare the effectiveness of zanamivir with oseltamivir for influenza A and B. METHODS: 1113 patients with influenza A or B were enrolled in the 2006-2007 influenza season. The duration of fever (temperature, >or=37.5 degrees C) and the percentage of patients afebrile at 24 and 48 h after the first dose of zanamivir or oseltamivir were calculated. Virus persistence after zanamivir therapy was also evaluated. RESULTS: There were marginally significant differences between the duration of fever after the first dose of zanamivir (31.8+/-18.4h) and oseltamivir (35.5+/-23.9h) for influenza A (p<0.05). The duration of fever after starting zanamivir therapy (35.8+/-22.4h) was significantly shorter than that of oseltamivir (52.7+/-31.3h) for influenza B (p<0.001). There were no significant differences between influenza A and B in the percentage of patients afebrile at 24 or 48 h after the first inhalation of zanamivir. The reisolation rate after zanamivir therapy showed marginally significant differences between influenza A and B (<0.05). By multiple regression analysis, therapy (zanamivir or oseltamivir) was the major determinant affecting the duration of fever for influenza B. CONCLUSION: Zanamivir therapy is more effective than oseltamivir for the treatment of influenza B infection.