Registered clinical evidence for ivermectin as a preventive antiviral: a landscape analysis of trials and the case for a nasally applied semisolid formulation
This landscape analysis of 437 registered clinical trials reveals that while oral ivermectin has failed to prevent COVID-19 due to insufficient respiratory concentrations, the hypothesis of using a locally applied nasal semisolid formulation for prevention remains entirely untested.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Viruses that cause respiratory illnesses, like the flu or the common cold, often begin their work in the nose. This is where they first land and start to multiply before moving deeper into the lungs. Because the nose is the front door, scientists have long wondered if applying medicine directly to the nasal lining could stop an infection before it takes hold. One drug, ivermectin, had shown promise in laboratory dishes by stopping viruses from copying themselves. However, when people took the drug as a pill, it did not seem to work in real-world trials. The leading explanation for this failure is that swallowing the drug sends only a tiny amount into the blood, and an even smaller amount reaches the delicate lining of the nose. If the drug never gets to the door in high enough numbers, it cannot stop the virus. This raises a specific question: could the drug work if it were applied directly to the nose, bypassing the stomach and the bloodstream entirely?
A team of researchers set out to find the answer by looking at the global record of clinical trials. They did not run a new experiment themselves; instead, they acted as detectives of the scientific record, searching through two massive international databases that track every medical study ever registered. They looked for every single study involving ivermectin to see what had actually been tested. Their goal was to determine if anyone had ever tried the specific idea of putting ivermectin directly into the nose to prevent infection, and if so, what happened. They examined hundreds of records, checking not just the title of the study but the fine print to see exactly how the drug was given and what the researchers hoped to achieve.
The search revealed a clear picture of what has been done and what has been missed. Of the hundreds of studies found, the vast majority focused on treating people who were already sick or on using the drug to treat parasitic worm infections. When the researchers looked specifically at studies designed to prevent a viral infection in healthy people, they found only a handful. More importantly, they found that none of these prevention studies had ever applied the drug to the nose. Every single prevention trial used pills or liquids swallowed by mouth. This means that the idea of using a nasal spray or ointment to stop the virus has never actually been tested in a formal medical study, despite being a logical solution to the problem of low drug levels in the nose.
The researchers also looked for any studies that did try to put ivermectin into the nose, regardless of whether they were trying to prevent or treat an infection. They found only five such studies registered in the databases. All five were aimed at treating people who were already infected or suffering from lingering symptoms like loss of smell, not at preventing infection in the first place. Furthermore, none of these studies used a thick, semi-solid ointment, which is the type of formulation that would stay in the nose long enough to be effective. Instead, they used sprays or drops, which wash out of the nose very quickly. Perhaps most telling, none of these five studies ever published their results. The data remains hidden, leaving scientists with no information on whether this approach is safe or feasible.
The team also compared ivermectin to other similar drugs to see if a different chemical might be a better candidate for a nasal treatment. They considered a drug called moxidectin, which is chemically related and stays in the body longer. However, they found that moxidectin would be a poor choice for a daily nasal treatment because it would build up in the body over time, potentially causing harm. They also looked at other related compounds but found that none of them had the necessary safety records or human testing data to be considered. Ivermectin remains the only drug in its class that has been proven safe for use on human skin and has a short duration in the body, making it the only realistic candidate for a repeated nasal application.
The final conclusion of this analysis is not that the drug works, but that the most promising way to test it has never been tried. The researchers emphasize that the failure of oral pills does not prove the drug is useless; it only proves that the pill is the wrong delivery method for this specific goal. They argue that a new type of study is needed, one that starts by testing if a thick nasal ointment can stay in the nose long enough without causing irritation, and if it can reach high enough concentrations inside the cells lining the nose. Only if those early safety and delivery tests succeed should a large-scale trial be launched to see if it actually prevents infection. Until such a study is done and its results are made public, the question of whether ivermectin can stop respiratory viruses at the door remains unanswered.
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