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Overdosing on Xofluza for Flu Led to Devastating Diarrhea

What happens when a doctor doesn't read dosing instructions? These patients suffered when they took the new antiviral drug Xofluza for flu. How good is it?

Did you know that there is a new flu drug in town? The FDA approved baloxavir (Xofluza) to treat influenza on October 24, 2018. In its announcement, the FDA stated “’This is the first new antiviral flu treatment with a novel mechanism of action approved by the FDA in nearly 20 years. With thousands of people getting the flu every year, and many people becoming seriously ill, having safe and effective treatment alternatives is critical. This novel drug provides an important, additional treatment option,’ said FDA Commissioner Scott Gottlieb, M.D.” Overdosing on Xofluza won’t improve its effectiveness, though, and may cause side effects, as this reader discovered. How good is Xofluza for flu?

Q. 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.

A. Baloxavir (Xofluza) is a brand new anti-viral flu medicine. This oral medication shortens the duration of flu symptoms when taken within 48 hours of getting sick.

We are puzzled why you took three doses, though. The advantage of this medicine is that it is given as a single dose. The triple dose might have increased your risk for diarrhea, a recognized side effect of Xofluza. The clinical trial data showed that three percent of people taking one pill suffered this complication.

Why do Americans Resist Oral Antiviral Drugs?

It comes as a great shock to most people to learn that oral antiviral medications have been available for over 50 years. Amantadine (Symmetrel) blocks the influenza A virus from replicating. It was first approved as an antiviral flu drug in 1966.

The drug never really caught on with physicians. That’s partly because the idea of an antiviral medicine was novel. In those days most medical students were taught that there were no effective antiviral medications.


Then came rimantadine (Flumadine). It was approved in 1994 and was safer than its cousin amantadine. It was prescribed more than amantadine, but never really took off either. Side effects were relatively uncommon. They included insomnia (2.1%), dizziness (1.9%), headache (1.4%), nervousness (1.3%), fatigue (1.0%), nausea (2.8%), vomiting (1.7%), dry mouth (1.5%) and weakness (1.4%).


When oseltamivir (Tamiflu) showed up in 1999 there still wasn’t a lot of excitement for oral antiviral flu medicine. Side effects such as nausea (10%), vomiting (8%) and headache (2%) didn’t instill enthusiasm. That and the fact that the clinical trials only seemed to demonstrate a one day reduction in time to improvement.

Learn More About Xofluza for Flu:

Here is a recent article you may find of interest:

What Should You Know About Xofluza Side Effects?

How Effective is Xofluza for Flu?

The FDA is uses language that is not very helpful when it comes to describing the efficacy of this drug. It refers to the results of two clinical trials this way:

“In both trials, XOFLUZA treatment at the recommended dose resulted in a statistically significant shorter time to alleviation of symptoms compared with placebo in the primary efficacy population.”

In an accompanying table the FDA notes that the “Time to Alleviation of Symptoms after Single Dose in Adult Subjects with Acute Uncomplicated Influenza in Trial 1 (Median Hours)” was:

50 hours for Xofluza for Flu vs 78 hours with Placebo for Flu

A trial in subjects 12 years of age and older the time to alleviate symptoms with Xofluza was 54 hours vs. 80 hours with placebo.

If you are not impressed by one less day of flu, how about preventing it in the first place? Here are some practical suggestions:

Can You Protect Yourself from the Flu?

Share your own flu experience in the comment section below. How do you protect yourself from coming down with influenza?

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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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