Ivermectin, a controversial antiparasitic drug that is being touted as a potential Covid-19 treatment, is not accelerating recovery in people with mild cases of the disease, according to a randomized controlled trial published in JAMA magazine on Thursday.
Ivermectin is commonly used to treat parasitic worms in humans and animals, but scientific evidence for its effectiveness against the coronavirus is sparse. Some studies have shown that the drug can prevent the recurrence of various viruses in cells. Last year, researchers in Australia found that high doses of ivermectin suppressed SARS-CoV-2, the virus that causes Covid-19, in cell cultures.
Such findings have prompted the use of the drug against Covid-19, especially in Latin America.
“Ivermectin is currently widely used,” said Dr. Eduardo López-Medina, a physician and researcher at the Center for Infectious Diseases in Cali, Colombia, who led the new trial. “In many countries in the Americas and other parts of the world, it is part of the national guidelines for the treatment of Covid.”
But the drug has also been shown to be divisive. While some scientists see potential, others suspect that the coronavirus can be effectively inhibited, but it may require very high doses. Health officials are also concerned that people desperate for coronavirus treatments may be taking versions of the remedy formulated for pets. (It is usually used to prevent heartworm in dogs.)
“There were many conflicting views on this, 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 very strict data to support their views. There are few well-controlled trials regarding the efficacy of the drug against Covid-19, although more are expected in the coming months. And the National Institutes of Health’s treatment guidelines point out that there is not enough evidence to recommend the drug in Covid-19 patients for or against it.
In the new study, dr. López-Medina and his colleagues more than 400 people who recently developed mild Covid-19 symptoms were randomly assigned to receive a five-day course of ivermectin or placebo. They found that Covid-19 symptoms lasted on average about 10 days among people who received the drug, compared to 12 days among those who received the placebo, a statistically insignificant difference.
The new trial adds much-needed clinical data to the debate over the use of the drug to treat Covid-19, said Dr. Regina Rabinovich, a global health researcher at the TH Chan School of Public Health in Harvard, said.
However, she noted that the trial was relatively small and did not answer the most urgent clinical question as to whether ivermectin could prevent serious illness or death. “Duration of symptoms may not be the most important thing to look at clinical or public health parameters,” she said.
The researchers found that seven patients in the placebo group deteriorated after enrolling in the study, compared with four in the ivermectin group, but the numbers were too small to draw a meaningful conclusion.
“There was a small signal there, and it would be interesting to see if the signal we saw is real or not,” said Dr. López-Medina said. “But that will have to be answered in a larger trial.”
Dr López-Medina also pointed out that the study population was relatively young and healthy, with an average age of 37 and few of the underlying conditions that could make Covid-19 more dangerous.
Larger trials, which are currently underway, may provide more definitive answers, says Dr. Rabinovich, noting that she is “completely neutral” about the potential usefulness of ivermectin. “I just want data because there’s such chaos in the field.”