What Older Adults Need to Know About Flu Antivirals

The medications can help quell symptoms and keep you out of the hospital

Kristen Fischer,

AARP

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Published September 26, 2025

AARP (Getty Images)

Even if you’re armed with a flu shot, wash your hands regularly and eat right, you can still become infected with influenza.

If that’s the case, antiviral medications may be able to offer some relief. Yet these drugs are largely underused, especially among older adults.

Antivirals can shorten your illness and reduce the risk of hospitalization or death from the flu, research shows — and that’s good news for people 65 and older, who are at higher risk for a bad case of the flu than younger patients. These medications can also lower your likelihood of experiencing flu symptoms and keep those symptoms from progressing.

Translation: Treating the flu with antivirals — and doing so soon after symptoms begin — can do more than get you back on your feet. These meds can literally keep you on your feet.

Which flu antivirals are available in the U.S.?

The antiviral medications on the market include:

Oseltamivir phosphate (Tamiflu): Available as a pill or liquid, this is approved for people 14 days old and older.
Zanamivir (Relenza): This is an inhaled medication for people age 7 and up. It’s not recommended for people with breathing problems like asthma or COPD.
Peramivir (Rapivab): A onetime intravenous treatment for individuals 6 months and older.
Baloxavir marboxil (Xofluza): A single-dose pill that’s approved for some children and everyone over the age of 12. It’s not ideal for complicated or progressive illness and isn’t recommended if you’re hospitalized.

Stay tuned for more: “Several new antivirals are in development, particularly long-acting agents and those targeting different viral mechanisms, though none are yet close to approval,” says Dr. Nadine Rouphael, a professor in the department of medicine at Emory University.

Why are flu antivirals helpful for older adults?

Older adults have a higher risk for complications from the virus. It’s estimated that between 70 and 85 percent of seasonal flu-related deaths and between 50 and 70 percent of flu-related hospitalizations occur in people 65 years and older. This is why the U.S. Centers for Disease Control and Prevention (CDC) recommends that older adults treat a flu infection with antivirals quickly when sick.

Not taking antiviral medications for flu is linked with increased risk of death, higher health care resource utilization and greater medical costs, according to a 2024 study of nearly 117,000 matched pairs of Medicare beneficiaries. And a 2020 report in Antiviral Research found that antiviral medications in hospitalized flu patients ages 65 to 74 lowered the risk of death.

A study published this year in Open Forum Infectious Diseases showed that oseltamivir lowered the risk of death in adults over 65 who had the flu. This was the case even when they took the drug 48 hours after symptoms began, whether they were vaccinated or not.

A JAMA Internal Medicine report published this year summarizing 73 existing trials that includes the four antivirals mentioned above showed that baloxavir seemed to be better at lowering the risk of hospital admission and likely lessened the time high-risk people with non-severe flu experienced symptoms.

How do flu antivirals work?

The first three antivirals — oseltamivir phosphate, zanamivir and peramivir — are neuraminidase inhibitors, which means they stop an enzyme called neuraminidase from releasing flu A and flu B virus particles in cells.

Baloxavir works differently against both main flu strains compared with the other antiviral drugs. It is a cap-dependent endonuclease inhibitor, which means that it blocks an enzyme used by the virus to make copies of itself.

When do I need to take an antiviral?

The drugs work best when taken within one to two days after symptoms begin, but they can be used after that time frame and still work well, especially if you’re at a higher risk of serious flu complications or are hospitalized with severe illness.

“The earlier you take them, the better the results,” says Andrew Pekosz, a flu researcher and professor of microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health.

To receive an antiviral prescription, you must have a positive flu test. Sometimes an at-home rapid test is enough, or you can get a test at your pharmacy or doctor’s office, Pekosz says.

Check with your pharmacy to see which options are in stock, he suggests. “That will make it easier for you to know which one you can go to if you need to fill your prescription quickly — and the earlier you take the antivirals, the better the outcome.”

Wondering when you can expect relief? According to the CDC, flu antivirals can shorten the time you’re sick by about one day.

Are some antivirals better for older adults than others?

All are effective, but baloxavir is the easiest to take as it’s only one pill on the first day you feel ill, says Pekosz. That said, it does have some limitations.

For example, it shouldn’t be taken with dairy products, calcium-fortified beverages, laxatives, antacids or certain supplements [containing calcium, iron, magnesium, aluminum, selenium or zinc],” says Dr. Wilbur H. Chen, an infectious disease physician-scientist and professor at the University of Maryland School of Medicine.

Oseltamivir (oral) is most commonly recommended for older adults due to its proven efficacy, ease of use, and longer safety track record, Rouphael notes.

Oseltamivir and peramivir are broken down in the kidneys, so people with kidney disease may require a smaller dose, Chen says.

Clinicians don’t recommend inhaled zanamivir for people with respiratory issues such as asthma or chronic obstructive pulmonary disease (COPD). It also shouldn’t be used with a nebulizer or in people on ventilators, Chen adds.

“I don’t think one is necessarily better than another, so long as they can be given appropriately and in a timely manner,” Chen says.

What are the side effects of antivirals?

Potential side effects depend on which medicine you take. Nausea and vomiting are most common with oseltamivir, while zanamivir can lead to difficulty breathing and Peramivir can cause diarrhea. The side effects of baloxavir can be similar to flu symptoms, and can include difficulty breathing, the CDC reports.

Each drug does have some warnings that come with it, so ask your doctor about the best choice for you, Pekosz says. Make sure your doctor knows about all the medications and supplements you take to avoid potential interactions, Rouphael adds.

Do antivirals work differently in older adults?

The mechanism of how antivirals work in older adults is the same as how they operate in younger folks. “There’s no real data suggesting age makes a difference in how well they work,” Pekosz adds.

But older adults may experience more gastrointestinal side effects (especially with oseltamivir), and dosing may need to be adjusted for those with kidney issues. Doctors may also monitor older adults for delirium or neuropsychiatric effects.

Can you just take an antiviral and skip the flu shot?

“Antivirals are not a substitute for vaccination,” Rouphael says. “The flu vaccine remains the most important tool for preventing illness in the first place.”

The CDC recommends higher-dose flu shots (including high-dose inactivated and recombinant vaccines) or adjuvanted inactivated flu vaccines for adults over the age of 65, compared to the standard-dose unadjuvanted flu vaccine.

Antivirals work regardless of whether you receive a flu vaccine, though vaccinated individuals may have a milder illness if they contract the flu, Rouphael says. “Antivirals reduce severity and complications in both groups,” she notes.

Even if the vaccine doesn’t fully prevent infection, it can reduce severity — and combining vaccination with timely antiviral treatment offers the best protection, especially for high-risk groups like those over 65, Rouphael says.

You may have to ask your primary care doctor to get an antiviral. Older adults and others at risk for severe flu complications often don’t receive antiviral drugs in urgent care and emergency department settings, according to a 2025 study in Clinical Infectious Diseases.

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Kristen Fischer is a contributing writer at AARP based at the Jersey Shore. She has also written for Health, WebMD, and McKnights and is the author of Zoo Zen: A Yoga Story for Kids.