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The Inside Story of Tamiflu Side Effects & Benefits

What's the story on drugs for influenza: Tamiflu (oseltamivir) and Xofluza (baloxavir)? What about Tamiflu side effects? Beware nausea!

One of the most familiar drugs for fighting influenza is Tamiflu (oseltamivir). Some people think it’s great. They believe it helps prevent family members from catching the flu when one person is sick as a dog. Others say it helps them get over the flu faster. Then there are those that say oseltamivir hardly makes a difference and Tamiflu side effects are nasty and not worth the benefit. What’s the straight and skinny on oseltamivir?

The Flu Will Be Back!

We reported that Australia is experiencing an early and intense flu season. That is after a couple of years of mild influenza outbreaks. The same was true in the US. Initially, the pandemic kept people home. They were also wearing masks. There was virtually no influenza from 2020 to 2022. Last winter there was a bit of an uptick, but nothing very bad.

What’s happening in Australia could be a forewarning of what we can expect in North America come this fall and winter. Many people will skip the influenza vaccine this fall. That is in part because there has been a big anti-vax movement building in the US. And many people hope that an oral drug like Tamiflu, will keep them from getting seriously ill.

How effective is oseltamivir in protecting people from a nasty flu attack? And what about Tamiflu side effects? Are the benefits worth the risks?

The Tamiflu Commercial:

If you haven’t seen this Tamiflu commercial, take a minute to watch it now. A very sick-looking man is seen creeping about in a very small house. He blows his nose with a teeny tissue. He’s so big he has to bend over to get into his tiny bathroom. The voiceover announcer says:

“Suffering from the flu is a really big deal. With aches, fever and chills there’s no such thing as a little flu. So why treat it like it’s a little cold? There’s something that works differently than over-the-counter remedies. Prescription Tamiflu attacks the flu virus at its source, so call your doctor right away.”

Oseltamivir is an oral antiviral medication that works by preventing the influenza virus from multiplying in the body, but there is a major controversy about the drug’s effectiveness. There is also the question of Tamiflu side effects!

The commercial warns about Tamiflu Side Effects:

“If you develop an allergic reaction, a severe rash or signs of unusual behavior, stop taking Tamiflu and call your doctor immediately. Children and adolescents in particular may be at an increased risk of seizures, confusion or abnormal behavior. The most common side effects are mild to moderate nausea and vomiting.”

How Tamiflu Works:

For the virus to penetrate human cells and then spread the infection to other cells throughout the body, it relies on an enzyme called neuraminidase (NA) that has a mushroom-like shape. The virus utilizes this enzyme to bust out of the host cell and spread lots more viruses (and chaos) throughout the body.

Tamiflu is an NA inhibitor. By blocking the NA enzyme the drug makes it harder for the influenza virus to escape a host cell and replicate.

As good as this sounds, you have to take the drug within the first day or two of symptoms. Once the flu takes hold, there are way too many viruses circulating in the body to stop the infection. For Tamiflu to work, you have to keep the number of infected cells under control so that the immune system won’t be overwhelmed.

How Well Does Tamiflu Work?

The Pros:

The crux of the Tamiflu controversy centers on the drug’s effectiveness. The Centers for Disease Control and Prevention (CDC) state that:

“Antiviral medications with activity against influenza viruses are an important adjunct to influenza vaccine in the control of influenza.”

Influenza vaccines are created anew each year, with the aim of matching that year’s circulating influenza virus strains. Flu viruses are notoriously given to mutation, and they change frequently. In 2014, for example, the vaccine against H3N2 (the predominant flu strain that year) was not a good match against the virus. It makes sense for the CDC to encourage other options in addition to vaccine. The public health experts there went on to say:

“Influenza antiviral prescription drugs can be used to treat influenza or to prevent influenza.”

They expected Tamiflu to reduce the severity of both type A and type B influenza and shorten the duration of the illness. Those who take the drug prophylactically (say when a spouse or child gets influenza) are supposed to be able to prevent the flu from taking hold in the first place.

The latest Study: Tamiflu’s Benefits and Side Effects:

A study published in JAMA Internal Medicine (June 12, 2023) has challenged the story that oseltamivir can be quite beneficial. Researchers gathered data from 15 randomized clinical trials comparing Tamiflu to placebo or nonactive controls.

The researchers introduce their meta-analysis this way:

“Before the COVID-19 pandemic, influenza was one of the most clinically burdensome respiratory viruses. The US Centers for Disease Control and Prevention estimated 29 million cases, 380 000 hospitalizations, and 28 000 deaths from influenza in the US during the 2018 to 2019 season. While COVID-19 led to a temporary reduction in infections, influenza is now expected to have a resurgence.”

If the Australian experience is valid, these investigators could be right on the money. That’s why their Tamiflu research is important for the coming flu season.

There were more than 6,000 adults or adolescents with confirmed influenza infections in this analysis. About 55% received a prescription for oseltamivir, but they were no less likely to need hospitalization than people given placebos:

“This systematic review and meta-analysis of oseltamivir for the outpatient treatment of laboratory-confirmed influenza included approximately 3400 more patients than prior analyses.Despite this, oseltamivir was not associated with significantly reduced hospitalization in general or in prespecified high-risk subgroups.”

Tamiflu Side Effects:

People taking this antiviral flu medicine were more likely to experience nausea and vomiting. The authors conclude that:

“…there is a lack of convincing evidence that oseltamivir reduces serious complications in outpatients with influenza, though its use is associated with an increase in nonsevere gastrointestinal adverse events.”

Contradictory Data:

A study published in The Lancet Respiratory Medicine (March 19, 2014) reported that Tamiflu was helpful during the 2009-1010 swine flu epidemic. The researchers evaluated data from dozens of studies involving nearly 30,000 patients who had been hospitalized with H1N1 influenza. These were severely ill people.

Those who received Tamiflu during their hospitalization were 25 percent less likely to die compared to patients who did not get the antiviral medication. If influenza-infected patients got Tamiflu within two days of the onset of symptoms, their likelihood of dying was halved. The lead investigator suggested that the earlier Tamiflu is used during an influenza epidemic, the more effective it will be in reducing severe illness or death.

A more recent study showed that oseltamivir is equally effective as a newer antiviral drug developed against influenza, zanamivir (Marty et al, The Lancet Respiratory Medicine, Feb. 2017). These were patients hospitalized with severe influenza. They responded to the drug in just over five days.

The Cons:

The Cochrane Collaboration is an independent network of health professionals who sift through scientific evidence to determine the safety and effectiveness of various treatments. On April 9, 2014, Cochrane researchers published a report in the BMJ on Tamiflu and another NA inhibitor called Relenza (zanamivir). The Cochrane Collaboration concluded:

“Compared with a placebo, taking Tamiflu led to a quicker alleviation of influenza-like symptoms of just half a day (from 7 days to 6.3 days) in adults, but the effect in children was more uncertain. There was no evidence of a reduction in hospitalisations or serious influenza complications; confirmed pneumonia, bronchitis, sinusitis or ear infection in either adults or children. Tamiflu also increased the risk of nausea and vomiting in adults by around 4 percent and in children by 5 percent. There was a reported increased risk of psychiatric events of around 1 percent when Tamiflu was used to prevent influenza.”

Tamiflu Side Effects:

  • Digestive upset (nausea, vomiting, diarrhea, stomach pain)
  • Headache
  • Nosebleeds
  • Psychiatric symptoms (hallucinations, abnormal behavior, self harm)
  • Skin reactions (any rash or allergic reaction must be reported immediately as it could become very serious)

One reader shares this story about Tamiflu side effects:

Q. I recently caught the flu and went to an urgent care center with a high fever. They tested me and said it was type A influenza.

I got a prescription for Tamiflu, but when I took two pills, I became so sick with diarrhea and vomiting that I stopped the Tamiflu. I preferred to let the flu run its miserable course. Who needs a double whammy of misery? I have heard that this reaction happens frequently.

A. Oseltamivir (Tamiflu) is one of several antiviral medications that can shorten the duration of illness. The official prescribing information lists nausea and vomiting as occurring between 8 and 10 percent of the time. When you have the flu, the last thing you need would be Tamiflu side effects such as nausea and vomiting!

Other readers have had a better experience with this drug. Here is one person’s report:

“I had the flu several years ago and was prescribed Tamiflu on the second day. Five pills cost $100. I stopped taking them after the third day because I felt so good. What a wonderful drug!”

These messages offer an example of the range of responses people may have to this medicine. To learn more about Tamiflu and other antivirals, you may wish to read our eGuide to Colds, Coughs & the Flu. This online resource may be found under the Health eGuides tab. It offers numerous nondrug approaches to respiratory infections as well.

A New Flu Drug: Xofluza (Baloxavir)

There’s a newer kid on the block. Baloxavir (Xofluza) is also advertising on television. This treatment for influenza was approved by the FDA in the fall of 2018. The commercials state:

“The flu sucks…everything out of you. The fever, aches and chills can flatten you fast. Prescription Xofluza can help you feel better in just over two days. Over-the-counter medicines just treat symptoms. Xofluza is different. It attacks the flu virus at its source with just 0ne dose…

“The most common side effects are bronchitis, nausea, diarrhea, sinusitis and headache.”

Xofluza is not cheap. Two pills (taken at the same time) could cost around $180. that’s the bad news. The good news is, that’s it! You only have to take one dose (two pills) and y0u are done. It’s still expensive.

How good is Xofluza? Well, it’s not magic. Here is what Consumer Reports (Oct. 25, 2018) had to say:

“The data from clinical trials suggest that Xofluza, approved for most healthy people over age 12, works about as well as oseltamivir (Tamiflu and generic)—the most commonly used flu treatment currently available—at reducing the length of a flu illness. Overall, both appear to cut the time people have flu symptoms from a little over three days to a little over two days.”

We told you. Xofluza is not a magic pill against influenza.

People’s Pharmacy Analysis

We are great admirers of the Cochrane Collaboration and we do not doubt that its analysis of Tamiflu was independent and objective. In the clinical trials that were analyzed, the drug only appeared to shorten the duration of the flu by about a day at best, and did not seem to prevent serious complications of influenza. That contradicts the conclusions of the study described above in The Lancet Respiratory Medicine.

We have used Tamiflu ourselves on several occasions and our subjective opinion is that the drug actually does speed healing and lesson symptoms. Personal experience, of course, is not scientific. Here are some other reports from visitors to our website:

D.P. writes:

“Twice in the last 10 years my husband was diagnosed with flu. A few days later I became ill with fever and flu symptoms. I went to the doctor and was given Tamiflu. I never got really sick. I was better in 48 hours; faster than my husband who was not given Tamiflu. (I think he will take it now if he gets it again.)”

Mel offers this story:

“When my son came down with R1N1 a few years ago, he was prescribed Tamiflu. As a child with Juvenile Idiopathic Arthritis he was in the ‘at risk’ category because he was taking immune suppressing drugs. Tamiflu worked well and he was better in about 1 ½ days.

“My daughter and I have asthma, and were also prescribed Tamiflu when we came down with the same virus. It worked well for us, too (2 days-4 days duration). As a mom, it was a big relief.”

J.E.C shared a similar experience:

” I had the same experience a few years ago. While my husband had suffered with severe flu symptoms for about a 2-week period, I called the doctor as soon as I became ill and was prescribed Tamiflu. My symptoms, which were much milder, only lasted about 2 days. I’m a believer – it’s good stuff.”

J.A.S. writes:

“I caught the flu several years back and was prescribed Tamiflu within 48 hours of my symptoms appearing. I absolutely HATE taking any prescription or OTC drugs, but I did take the Tamiflu not knowing anything about it at that time.

“My symptoms lessened promptly and I felt better so quickly I was very surprised. Perhaps I had a mild case of the flu, but I do remember that Tamiflu had a relatively quick response and seemed to have stopped this flu infection dead in its tracks. I doubt if it was a placebo effect because I was soooo reluctant to take it and didn’t exactly have a positive outlook about it.”

Xofluza Stories:

Lonny is pretty cynical:

“The side effects of the flu drugs are the symptoms of the flu. So if you don’t feel bad enough already, you can take a drug to make you feel worse. And pay a small fortune for the drug. Sounds to me like an advanced case of stupidity.”

Linda and her husband weren’t thrilled with the outcome:

“My husband and I returned from a trip to Europe with a strain of the flu apparently not covered by our flu vaccine. We took Xofluza and after three doses, both of us developed diarrhea and abdominal cramping. We stopped taking the meds, and the symptoms stopped. The headache, congestion, and body aches of the flu were bad enough without adding the diarrhea caused by expensive meds.”

The Bottom Line on Tamiflu Side Effects & Xofluza:

Tamiflu is not a miracle medicine against influenza. Neither is Xofluza. The clinical trial data suggest that these drugs are modestly effective at shortening the duration of the flu.

They do have side effects (predominately digestive in nature). According to Cochrane, about 4 to 5 percent of people taking Tamiflu experienced nausea or vomiting and about 1 percent developed psychological side effects when they took the drug to prevent the flu. Some people find that the Tamiflu side effects are worse than the flu.

That said, there is evidence that people do benefit from Tamiflu and Xofluza, especially when these drugs are taken as soon as possible after developing symptoms. If the vaccine does not live up to expectations, Tamiflu or Xofluza may be worth consideration in the fight against influenza.

We think you will find this article about the science behind Vicks VapoRub on the soles of your feet to calm a nighttime cough of great interest. You may also find our article about how to make onion syrup for a cough intriguing.

If you would like to read about some other options, you may find our Guide to Colds, Coughs & the Flu of interest.

photo credit: ahisgett via photopin cc

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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