Do I Need Antiviral Drugs If I Have the Flu?

Updated October 28, 2024

Just as antibiotics fight bacterial infections, so do antiviral drugs fight viral infections. Bacteria and viruses are very different organisms, and drugs that treat one do not treat the other. Three antiviral drugs, oseltamivir (Tamiflu) and baloxavir marboxil (Xofluza), pillstaken by mouth, and zanamivir (Relenza), an inhaled medication, are particularly effective against the influenza viruses that cause the flu.

All of these antivirals work only if taken within 48 hours of developing symptoms of the flu. Fever, headache, body aches, sore throat, and cough are all classic symptoms of the flu. If you start taking one of these medications within that 48-hour window, the benefits include:

• A shorter duration of illness (typically about one day shorter)
• A shorter period in which you will be contagious and can spread the disease to others
• A possible lowered risk of developing complications from the flu, although evidence is mixed for how effective antivirals are for preventing complications

The major complication is pneumonia. Pneumonia caused by the flu virus itself is, fortunately, very rare. It’s characterized by a persistent fever, shortness of breath and lots of phlegm. Sometimes, bacteria make their way into lungs already vulnerable from the effects of the flu virus. In this scenario, patients start to get better, but then fever returns, along with the production of thick, discolored phlegm, and progressive shortness of breath. People with these symptomsusually require a chest x-ray and sometimes antibiotic therapy. There is a third pattern–a combination of the two types just described–which almost always requires hospitalization.

No one is impervious to these complications of the flu, but certain people are at increased risk, including those with: serious underlying health issues, such impaired immunity (from illness or certain medications); chronic lung disease; chronic heart disease; asthma; malignancy; poorly controlled diabetes; chronic kidney disease; and other debilitating illnesses. Pregnant women in their second and third trimesters are also at increased risk, as are very young children and the elderly.

Generally, health care providers may recommend antiviral medications for people at high risk of developing flu-related complications or for people with severe symptoms. Be sure to talk to your health care provider to ensure you have all the information you need to make an informed decision.

Preventive therapy with antiviral drugs may be helpful for some people who have been exposed to the flu, but don’t have symptoms. People who may benefit from preventive therapy include those at high risk for developing complications, and those who are unvaccinated and have close contact with someone who is at high risk for complications. The antiviral medication dose is different than it is for someone who has been infected, so talk to your healthcare provider if you have symptoms of the flu.

Some people experience no side effects at all. With Tamiflu and Xofluza, the most common side effects are gastrointestinal, such as nausea and vomiting, . With Relenza, the inhaled medication, the most common side effect is spasm of your large airways that can mimic asthma; however, this generally only occurs in people with pre-existing asthma or underlying chronic lung disease. Uncommon but serious side effects of Tamiflu and Relenza include seizures and other neurologic and psychiatric side effects such as suicidal thoughts and hallucinations.

The standard course is five days for Tamiflu and Relenza. Tamiflu is a pill that you take twice a day, and Relenza is an inhalant, which you take two times, twice a day. Xofluza is a one-time dose. If you have kidney problems, your health care provider may have to adjust the dose. Other dosage adjustments are made for young children.

Don’t worry; most people recover well from the flu within a couple of weeks without treatment. It’s generally recommended that you should not take antiviral medications if you have had symptoms for longer than 48 hours. The antiviral medications will not be effective and you won’t experience any of the benefits mentioned above. Stay home, rest, and the worst symptoms will usually resolve within several days to a week. If, after a few days, you aren’t getting better–and particularly if you’re getting worse–contact your primary health care provider.