Cyclophosphamide treatment has been used to immunosuppress mice to assess the efficacy of a neuraminidase inhibitor (peramivir) in an immunocompromised host (Sidwell et al., 2003). Cyclophosphamide was injected intraperitoneally at a dose of 100 mg/kg every 4 days for varying lengths of time. Peramivir was capable of significantly ameliorating the influenza virus infection in mice immunosuppressed by short-term or prolonged cyclophosphamide therapy.