The aim of this work is to evaluate the efficacy of zanamivir in the treatment and prevention of influenza. This drug is a neuraminidase inhibitor that is effective against both A and B influenza viruses. Five randomized, double-blind, placebo-controlled, clinical trials have been published, showing a reduction in the duration of flu symptoms between 1 and 2.5 days. A greater benefit is seen in the patients with influenza-confirmed infection, with fever and when the treatment begins in the first 30-36 hours. For the prevention of influenza, two placebo-controlled clinical trials have been published, where flu incidence was reduced by 50-67%. The characteristics of zanamivir (efficacy, safety and lack of resistance) make it an appropriate option for subjects not protected by vaccination and for those with high risk of complications.