The antiparasitic drug ivermectin, which has risen in popularity as an alternative treatment for Covid-19 despite a lack of strong research to back it up, showed no signs of alleviating the disease, according to the results of a large clinical trial published Wednesday. . †
The study, which compared more than 1,300 people infected with the coronavirus in Brazil who received either ivermectin or a placebo, effectively ruled out the drug as a treatment for Covid, the study authors said.
The researchers shared a summary of these results in August at an online presentation hosted by the National Institutes of Health, but the full dataset had not yet been published in The New England Journal of Medicine.
“Now that people can dive into the details and the data, hopefully that will lead the majority of doctors away from ivermectin to other therapies,” said Dr. David Boulware, an infectious disease expert at the University of Minnesota.
Ivermectin has been widely used to treat parasitic infections for decades. Early in the pandemic, as researchers tried thousands of ancient drugs against Covid-19, lab experiments with cells suggested that ivermectin could block the coronavirus — albeit at much higher concentrations than would be safe for human use.
Some small studies suggested possible benefits in humans, but later analysis found that the studies were flawed and the benefits illusory. The clinical trial whose data was published Wednesday was much larger and more rigorous.
Researchers in Brazil provided the drug to 679 patients over the course of three days between March and August 2021 in a double-blind treatment, meaning neither the patients nor the medical staff knew whether a particular patient was receiving a Covid treatment drug or a placebo.
The results were clear: taking ivermectin did not reduce a Covid patient’s risk of ending up in hospital.
The researchers focused on different groups of volunteers to see if they experienced benefits that others did not. For example, it might have been possible for ivermectin to work only if taken early in an infection. But volunteers who took ivermectin in the first three days after a positive coronavirus test were found to have worse results than those in the placebo group.
There are other large randomized trials of ivermectin, with thousands of volunteers, still ongoing and yet to share their results. The National Center for Advancing Translational Sciences, which is part of the NIH, has been conducting one close study of ivermectin and several other drugs for Covid patients for more than a year, with results not yet released.