There are two groups of Food and Drug Administration (FDA) approved antiviral drugs available for prevention and treatment of influenza in people: Neuraminidase Inhibitors (NIs) and M2 Inhibitors.
M2 Inhibitors: An older class of antiviral drugs, the M2 inhibitors such as amantadine and rimantadine, could potentially be used against pandemic influenza, but resistance to these drugs can develop rapidly and this could significantly limit their effectiveness against pandemic influenza. Some currently circulating H5N1 strains are fully resistant to the M2 inhibitors. However, should a new virus emerge through reassortment, the M2 inhibitors might be effective.
Neuraminidase Inhibitors (NIs): The World Health Organization (WHO) considers NIs to be the major class of antiviral agents for prevention and treatment of H5N1 infection. NIs include oseltamivir (TAMIFLU®) and zanamivir (RELENZA®). Both are taken by mouth and help reduce the severity and duration of illness caused by an influenza virus. The efficacy of NIs depends on early administration, ideally within 48 hours after symptom onset.
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