Nikhil Prasad Fact checked by:Thailand Medical News Team Dec 14, 2025 7 hours, 39 minutes ago
Medical News: A Natural Option to Prevent Influenza May Be Closer Than Expected
A new observational study conducted in Bulgaria suggests that the common and inexpensive cough medicine bromhexine hydrochloride (BRH) may offer significant protection against influenza when used prophylactically. Inspired by earlier success in COVID-19 prevention, researchers from multiple departments at Medical University–Sofia and regional hospitals conducted a pilot survey on its possible role in flu prevention. This
Medical News report looks at the findings in more detail.
Bromhexine may help prevent flu infections when taken daily before the season begins
The Study at a Glance
Researchers from the Research Institute of Innovative Medical Science and several faculties at Medical University–Sofia recruited over 400 participants, most of whom were over 60 years old. These participants voluntarily took BRH tablets—8 mg twice daily—for at least three weeks leading up to flu season. On average, they took the drug for 80 days. The participants had nearly one comorbidity each on average, with some having up to seven health conditions.
Surprisingly, only 10.6% of those using BRH reported getting influenza. That number is far lower than the national flu rate in Bulgaria for 2023, which was recorded at 36.15%. Even when compared with a conservative national flu-only rate of 15%, the results remained statistically significant.
Bromhexine demonstrated prophylactic properties against flu infections including those by H1N1 or H3N2 strains.
Why BRH Might Be Effective
Bromhexine hydrochloride is not just a simple cough suppressant. It is also a known inhibitor of TMPRSS2—a cellular enzyme essential for the entry of both influenza and SARS-CoV-2 viruses into lung cells. By blocking this enzyme, BRH may prevent the viruses from establishing infection in the body. The drug is derived from a plant called Adhatoda vasica and has been in use since the 1960s. It is cheap, widely available, and has a strong safety record, even with long-term use.
Researchers note that the most effective use of BRH is before exposure to the virus. If used during or after infection, its effectiveness drops significantly. The study also highlighted that while age is typically a major risk factor for flu, it had no noticeable effect among those taking BRH—suggesting the drug might level the playing field for older individuals.
Key Findings and Statistical Insights
-Average age of participants: 58.9 years
-Mean duration of BRH use: 80 days
-National flu rate: 36.15%
-Flu rate in BRH users: 10.6%
-Risk reduction increased with longer BRH use
Comorbidities remained the strongest risk factor for infection
Logistic regression showed that each additional comorbidity nearly doubled the risk of flu, while every 10 extra days of BRH intake reduced risk by about 1%.
Potential Implications for Flu Seasons Ahead
These results offer a compelling argument for further study into bromhexine as a low-cost, widely accessible prophylactic agent against influenza. Unlike vaccines, which require annual updates and face compliance issues, BRH could provide a simpler and more consistent line of defense—especially for vulnerable populations. However, researchers caution that the results are based on self-reported data and need further verification through laboratory-based trials.
With both influenza and COVID-19 expected to co-circulate for years to come, and with TMPRSS2 acting as a shared gateway for both viruses, BRH might serve as a multipurpose shield. The study authors hope their findings will spark wider discussions and more formal investigations into this overlooked drug.
The study findings were published on a preprint server and are currently being peer-reviewed
https://www.preprints.org/manuscript/202511.1871
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Medical News.
Read Also:
https://www.thailandmedical.news/articles/influenza-or-flu
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