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August 05, 2005

Virulence may determine the necessary duration and dosage of oseltamivir treatment for highly pathogenic a/vietnam/1203/04 influenza virus in mice.

J Infect Dis. 2005 Aug 15; 192(4): 665-72
Yen HL, Monto AS, Webster RG, Govorkova EA

Background. Control of highly pathogenic avian H5N1 influenza viruses is a major public-health concern. Antiviral drugs could be the only option early in the pandemic.Methods. BALB/c mice were given oseltamivir (0.1, 1, or 10 mg/kg/day) twice daily by oral gavage; the first dose was given 4 h before inoculation with H5N1 A/Vietnam/1203/04 (VN1203/04) virus. Five- and 8-day regimens were evaluated.Results. Oseltamivir produced a dose-dependent antiviral effect against VN1203/04 in vivo (P<.01). The 5-day regimen at 10 mg/kg/day protected 50% of mice; deaths in this treatment group were delayed and indicated the replication of residual virus after the completion of treatment. Eight-day regimens improved oseltamivir efficacy, and dosages of 1 and 10 mg/kg/day significantly reduced virus titers in organs and provided 60% and 80% survival rates, respectively (P<.05). Overall, the efficacy of the 5- and 8-day regimens differed significantly (death hazard ratio, 2.658; P<.01). The new H5N1 antigenic variant VN1203/04 was more pathogenic in mice than was A/HK/156/97 virus, and a prolonged and higher-dose oseltamivir regimen may be required for the most beneficial antiviral effect.Conclusions. Oseltamivir prophylaxis is efficacious against lethal challenge with VN1203/04 virus in mice. Viral virulence may affect the antiviral treatment schedule.

Posted by dymaxion at August 5, 2005 02:25 PM

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