Zanamivir is an antiviral drug used to treat and prevent influenza A and B. It works by inhibiting the neuraminidase protein of the influenza virus, preventing it from spreading between cells. Common side effects include weakness, headache, fever, cough, runny nose and sore throat, which may be reduced by 1 to 1.5 days with treatment. It is administered through oral inhalation twice daily for 5 days for treatment or once daily for prevention.