Tamiflu: Should You Worry About Side Effects?

If you have the flu, this antiviral drug can be a big help—but some serious side effects have been reported.

hands opening a pill pack

Updated on January 10, 2024.

Year in and year out, the flu remains a big-time health concern for healthcare providers and patients. You can catch the illness any time of year, but flu season typically begins in October and peaks between the months of December and February. And as you likely know, the flu can cause some pesky symptoms, such as a fever, cough, sore throat, and fatigue. It can also lead to more serious complications, like pneumonia.   

If you become sick with the flu, speak with a healthcare provider as soon as possible. You can ask for an antiviral drug prescription, which could shorten the misery. Medication is most effective for people who take it within 48 hours of having symptoms.

That said, you may have heard some scary stuff about the most popular antiviral, Tamiflu (oseltamivir). There have been some reports over the years that it may spark hallucinations and unusual, even life-threatening behavior.

Are side effects like these really something to worry about? Here's what you should know about this antiviral medication—and how to put it all into perspective.

Your antiviral options

Four antiviral drugs to treat the flu are approved by the U.S. Food and Drug Administration (FDA) and recommended by the Centers for Disease Control and Prevention (CDC). They are:

  • Oseltamivir (Tamiflu)
  • Zanamivir (Relenza)
  • Peramivir (Rapivab)
  • Baloxavir marboxil (Xofluza)

Of these, Tamiflu is the most popular, according to Amesh Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security and a spokesperson for the Infectious Diseases Society of America. It can be given in liquid or capsule form. A generic version of oseltamivir is also available.

Relenza comes in inhaler form and can be cumbersome to use, he says. Rapivab is given intravenously, usually to someone so sick they can't take medicine by mouth. Xofluza is a pill given as a single dose. Two other antiviral drugs, amantadine (generic) and rimantadine (Flumadine and generic versions) have been approved by the FDA, but the CDC doesn't currently recommend them, as they don't work well against the flu viruses that have been circulating in recent years.

What Tamiflu does

Tamiflu works by blocking the action of an enzyme on the surface of the flu virus, restraining the virus from spreading to other cells, according to Genentech, its inventor.

Tamiflu isn't just meant for people who want to shorten the time they’re sick—though it can reduce the course of the flu by about a day. It is recommended in particular for those at risk of complications of the flu. This includes babies, young children, older adults, pregnant people, nursing home residents, and those with other major health issues, like heart disease or diabetes.

The drug may help prevent ear infections in children, for example. It may also help avert pneumonia—and even death—in adults, according to the CDC. Healthcare providers use their judgment in prescribing it to otherwise healthy people.

The lowdown on side effects

"In general, Tamiflu is a well-tolerated drug," Dr. Adalja says. Nausea, vomiting, and headaches are the most common side effects of oseltamivir; you can be given additional medicine to ease the vomiting. Taking it with food may also ease gastrointestinal issues. There have, however, been rare reports of hallucinations, confusion, and other unusual behavior, which are of concern to patients and providers.

In 2018, an Indiana family reportedly blamed the drug for the suicide of their teenaged son. That same year, a family in Texas told the media that their daughter, after taking Tamiflu, began hallucinating and was about to jump out a window when her mother rescued her.

Earlier, in 2005, the FDA had reviewed reports of 12 pediatric deaths in Japan since Tamiflu's approval. The agency concluded that the evidence could not prove the drug was responsible due to the children's other medical conditions and additional medications, as well as not enough reported details. Genentech says there hasn't been a connection established between Tamiflu and the events.

Genentech warns that those with flu, especially children and teens, may be at an increased risk of seizures, confusion, or abnormal behavior soon after they get sick. These side effects may occur after starting to take Tamiflu, or they may start when the patient has the flu but doesn't take Tamiflu, the company has noted.

Adalja agrees that no cause and effect can be proven. It is possible, he says, that something about having the flu by itself may trigger these reactions in some people, with members of younger age groups perhaps being more vulnerable.

What's more, Adalja says he has never seen cases of psychiatric side effects from Tamiflu. "I am a pretty liberal prescriber of Tamiflu," he adds. ''We do know Tamiflu is very well tolerated by the vast majority of people." In fact, in a March 2018 study published in Annals of Family Medicine, researchers found no connection between Tamiflu and suicide in pediatric patients. A Korean study published in 2020 in Clinical Infectious Diseases derived similar results.

Even so, Adalja says, if you take the drug, you should be sure someone watches you for signs of abnormal behavior. If any worrisome or unusual behavior occurs, such as talk of self-harm, get medical help right away. You can also call or text the 988 Suicide and Crisis Lifeline for help.

Article sources open article sources

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Centers for Disease Control and Prevention. Influenza (Flu): Flu Season. Reviewed September 20, 2022.
Centers for Disease Control and Prevention. Influenza Antiviral Medications: Summary for Clinicians. December 8, 2023. 
Yahoo Life. Doctors say nightmares on Tamiflu are ‘very common’ — here’s what you need to know .January 15, 2019.
The Medical Letter. Antiviral Drugs for Influenza for 2023-2024. November 13, 2023.
Centers for Disease Control and Prevention. Influenza Antiviral Medications. September 8, 2022. 
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