Flu Antiviral Drugs: Who Should Take Them, Which Ones, and When

Flu antiviral drugs are prescription medicines that fight flu viruses in the body. They come as pills, liquids, an inhaled powder or an intravenous solution. None is sold over the counter; they are available only with a prescription from a health care provider.

They are not antibiotics, which fight bacteria. Flu antivirals treat only flu, and they are different from the antivirals used for other infections such as COVID-19 — the drugs prescribed for COVID-19 are not approved or recommended for flu.

What they do

Flu antivirals can ease symptoms and shorten the illness by about a day. Started soon after symptoms begin, they can also help reduce some flu complications. For adults in hospital with flu, some studies have found that early treatment can shorten the hospital stay and lower the risk of death.

Timing is everything. They work best when started within 1 to 2 days of the first symptoms. Starting later can still help, though, especially for someone at higher risk of serious complications or in hospital with severe illness.

The four recommended drugs

CDC recommends four drugs approved by the Food and Drug Administration (FDA) for treating flu:

• Zanamivir is taken with an inhaler and is not recommended for people with breathing problems such as asthma or COPD.
• Baloxavir is also approved to prevent flu in people 5 and older after contact with someone who has it. It is not recommended during pregnancy or breastfeeding, or for outpatients with complicated or progressive illness, because there is no information on its use in them — nor, given limited data, for patients in hospital.

Who should take them

Antivirals should be started as soon as possible for:

• anyone in hospital with flu;
• anyone very sick with flu who does not need hospital care; and
• anyone at higher risk of serious complications, because of age or an underlying condition, who develops flu symptoms — people with asthma or chronic lung disease, diabetes (including gestational diabetes) or heart disease, and pregnant women among them.

People at higher risk who develop flu symptoms should contact their doctor promptly. People with mild illness who are not at higher risk may also be treated, but most do not need to be.

Children

Antivirals are a safe and effective option for children with flu, ideally started within two days of falling ill and usually taken for five days. Which drug depends on age. CDC recommends oseltamivir from birth, and the American Academy of Pediatrics from 2 weeks of age; it comes as a liquid for children. Zanamivir is approved from age 7 but not recommended for children with asthma or other chronic lung disease; peramivir from 6 months; and baloxavir, as a single tablet, from age 5.

If a child is prescribed oseltamivir capsules but cannot swallow them and the liquid is unavailable, the capsules can be opened and mixed with a thick, sweetened liquid.

Pregnancy

Oral oseltamivir is the recommended treatment during pregnancy, because it has more studies suggesting it is safe and beneficial in pregnancy than any other recommended antiviral.

Side effects

They vary by drug. Oseltamivir most often causes nausea and vomiting; zanamivir can cause bronchospasm, difficulty breathing with wheezing; and peramivir can cause diarrhea. Less common side effects have also been reported. A provider, or the FDA’s drug information with each manufacturer’s package insert, can give details. Take each drug exactly as prescribed — the dose, how often and for how long.

Antibiotics will not help

When antibiotics are not needed they do no good, and their side effects can still do harm — from a mild rash to severe allergic reactions, antimicrobial-resistant infections and C. diff infection, whose diarrhea can lead to severe colon damage and death.

Not a substitute for vaccination

Antivirals are a second line of defense, for treating flu — seasonal or novel — once someone is sick. The best way to prevent flu and its serious complications is a flu vaccine, even though its effectiveness varies from season to season. Everyone 6 months and older should get one every year.

Sources

Based on "Treating Flu with Antiviral Drugs," Centers for Disease Control and Prevention; a work of the United States government in the public domain.