Ivermectin, a controversial anti-parasitic drug that has been touted as having potential Covid-19 treatment, does not speed recovery in people with mild cases of the disease, according to A Randomized Controlled Study published on Thursday in JAMA magazine.
Ivermectin is typically used to treat parasitic worms in both humans and animals, but the scientific evidence of its effectiveness against the coronavirus is thin. Some studies have shown that the drug can prevent several different viruses from replicating in cells. And last year Researchers found in Australia that high doses of ivermectin suppressed SARS-CoV-2, the virus that causes Covid-19, in cell cultures.
Such findings had stimulated the use of the drug against Covid-19, especially in Latin America.
“Ivermectin is currently used extensively,” said Dr. Eduardo López-Medina, doctor and researcher at the Center for Pediatric Infectious Diseases in Cali, Colombia, who led the new study. “In many countries in the Americas and other parts of the world, this is part of national guidelines for treating Covid.”
But the drug has also been shown to be divisive. While some scientists see potential, others suspect that effective inhibition of the coronavirus could require extremely high, potentially unsafe doses. Health officials have also feared that people desperate for coronavirus treatments might be taking versions of the drug formulated for pets. (It’s often used to prevent heartworms in dogs.)
“There have been many conflicting views on these, sometimes extremely conflicting views,” said Dr. Carlos Chaccour, a researcher at the Barcelona Institute for Global Health who was not involved in the new study. “I think it’s become another hydroxychloroquine.”
But neither the proponents nor the critics had much rigorous data to support their views. There are few well-controlled studies on the drug’s effectiveness against Covid-19, although more are expected in the coming months. And treatment guidelines from the National Institutes of Health state that they exist not enough evidence “For or against” the use of the drug in Covid-19 patients to be recommended.
In the new study, Dr. López-Medina and his colleagues happened to admit more than 400 people who had recently developed mild Covid-19 symptoms to receive five-day treatment with ivermectin or a placebo. They found that Covid-19 symptoms lasted an average of about 10 days in people who received the drug, compared to 12 days in those who received the placebo, a statistically insignificant difference.
The new study adds much-needed clinical data to the debate over the drug’s use to treat Covid-19, said Dr. Regina Rabinovich, a global health researcher at Harvard’s T.H. Chan School of Public Health, which was not involved in the study.
However, she noted that the study was relatively small and didn’t answer the most pressing clinical question of whether ivermectin can prevent serious illness or death. “Duration of symptoms may not be the most important clinical or health parameter,” she said.
The researchers found that seven patients in the placebo group got worse after entering the study compared to four in the ivermectin group, but the numbers were too small to make a meaningful conclusion.
“There was a little signal there and it would be interesting to see if this signal we saw is real or not,” said Dr. López Medina. “But that would have to be answered in a larger process.”
Dr. López-Medina also pointed out that the study population was relatively young and healthy, with an average age of 37 and few underlying diseases that can make Covid-19 more dangerous.
Larger studies currently in progress could provide more definitive answers, said Dr. Rabinovich, who stated that she was “completely neutral” about the potential benefits of ivermectin. “I only want data because the field is so chaotic.”