Tamiflu or Xofluza

As I’m shut in on this cold Sunday afternoon due to the “inclement weather” Atlanta is experiencing, I thought I’d take a moment to reflect on my winter break when I was unfortunately stricken with the flu (luckily after our trip to Colorado).

The flu, otherwise known as influenza, is a viral respiratory infection affecting the nose, throat, and obviously, lungs. Typically I’d just shrug it off as I had gotten the annual vaccine, yet for some reason it felt as if I had no protection against it whatsoever. Turns out there was a new variant of the flu, a supposed “super flu,” that was able to evade the immunity provided by the flu shot. Subclade K, the “super flu,” is a mutation of the influenza A virus, and this mutation has enabled the virus to appear as a mismatch with the traditional flu vaccine.

Ultimately, I went to the doctor’s office and thats when I encountered something interesting…

After being tested for both the flu and COVID, I was diagnosed with the flu (expected), and prescribed two potential antiviral medications: Tamiflu (which I was quite familiar with), but also Xofluza (what is this?).

Tamiflu, or oseltamivir phosphate, which had been the traditional antiviral drug prescribed to combat the flu, is a 5 day long course of pills that works by inhibiting the spread of the virus within the body. Specifically, it inhibits the enzyme neuraminidase, which is used by the virus to free itself from the host cell after replication in order to infect another healthy cell. Tamiflu comes in and binds to this enzyme, essentially forcing to virus to remain stuck within the host cell, thus preventing its spread to other cells.

On the other hand, Xofluza, or baloxavir marboxil, is only one singular pill that works by stopping the virus from being able to replicate. Rather than inhibiting the mechanism that allows the flu virus to hop from cell to cell, Xofluza inhibits the polymerase acidic endonuclease enzyme, preventing the virus from copying its genetic material and thus preventing new copies of the virus from being made. This enzyme is necessary for the virus to replicate its genetic material as it takes a part of the host’s genetic material (a cap) and uses it to replicate. Without it, the virus is essentially nullified and fails to convert the healthy host cell into a “virus factory.”

Since Xofluza targets the very mechanism for replication, its positive effects appear much sooner than Tamiflu which still enables replication but just prevents its spread. In the case of Tamiflu, it may take around 3 days for flu symptoms to reduce, whereas Xofluza, for me personally, reduced symptoms within a few hours of ingestion.

Apart from the science behind these drugs, there’s also a social and economic factor in determining which is the better choice. Tamiflu can be taken as young as 2 weeks old, is cheaper and covered by most insurances, and is more heavily researched. Xofluza, as it’s newer, has only been approved for those as young as 5 years old, and is generally more expensive due to it being a branded medication.

With time comes more research, and with more research we may see differing results that may skew the choice to one or the other. However for now, either of the options would make a fine choice, but the more important lesson to take away is to take care of preventative measures such as getting the seasonal vaccine, maintaining proper hygeine in public spaces, and utilizing PPE in high-risk-of-infection areas.

[1] CDC. (2024, September 11). Treating Flu with Antiviral Drugs. Influenza (Flu). https://www.cdc.gov/flu/treatment/antiviral-drugs.html

[2] Ng, K. E. (2019). Xofluza (Baloxavir Marboxil) for the Treatment Of Acute Uncomplicated Influenza. Pharmacy and Therapeutics, 44(1), 9. https://pmc.ncbi.nlm.nih.gov/articles/PMC6336199/

[3] Baker, J. B., Block, S. L., Cagas, S. E., Macutkiewicz, L. B., Collins, C., Sadeghi, M., Sarkar, S., & Williams, S. (2023). Safety and Efficacy of Baloxavir Marboxil in Influenza-infected Children 5–11 Years of Age: A Post Hoc Analysis of a Phase 3 Study. The Pediatric Infectious Disease Journal, 42(11), 983–989. https://doi.org/10.1097/INF.0000000000004062