Oseltamivir (Tamiflu) and zanamivir (Relenza) are both prescription antiviral medicines that may shorten the duration of flu by 1 day. You must begin taking oseltamivir or zanamivir within 48 hours of onset of flu symptoms. You'll take the medicine for 5 days. See our FAQs for information about how they work.
Oseltamivir and zanamivir are generally safe but they can also cause serious side effects, including but not limited to allergic reaction, severe skin reactions, gastrointestinal bleeding, liver inflammation, seizures, delirium, behavior changes, and altered mental status. Read the package insert that comes with the medicine for a full list of side effects and warnings.
We diagnose the flu based on your symptoms, but there's always a risk of misdiagnosis. We only prescribe a treatment when it's appropriate based on evidence-based guidelines.
If we treat you for the flu even though you don't have it, you'd be taking an antiviral unnecessarily and taking on the small risk of side effects from the medicine without any clear benefit. There's also a risk that the medicine we prescribe won't work, even if we correctly diagnosed you with the flu.
Even if you have the flu, our decision to treat you with antiviral medicine depends on a number of factors, including your medical history and the infection risk based on where you live. Other providers may elect to treat cases of flu that we do not. If we decide not to treat you, we'll tell you when you should seek care from a doctor or nurse practitioner in person.
Whether we decide to treat you or not, you have the right to decline our recommended treatment plan and seek care from another doctor or nurse practitioner.