The largest study yet on the efficacy of horse dewormer and quack-right favorite ivermectin on COVID-19 finds zero benefit as either prevention or as a cure for the virus.
The antiparasitic drug ivermectin doesn't prevent severe disease from Covid-19 any more effectively than symptom management and close observation by medical professionals, according to a study published Friday in the journal JAMA Internal Medicine.
The study enrolled nearly 500 people 50 and older who were at risk of severe Covid-19 because of their age and underlying health. These patients were treated at 20 public hospitals and a quarantine center in Malaysia in 2021.
Half of the patients took a relatively high dose of oral ivermectin for five days, and the other half -- the comparison group -- received treatment for their symptoms, such as fever-reducing medications. All were monitored for progression of disease.
There was no difference in outcomes between the groups. In fact, slightly more patients in the ivermectin group went on to need extra oxygen compared with those who took a placebo, though the difference was not statistically significant.
This was the main outcome researchers studied, but they also looked at whether patients needed to be hospitalized, had to go on a ventilator, needed intensive care or died from their infections. There was no meaningful difference in outcomes between the group that took ivermectin and those who got the placebo treatment.
The study had several important strengths:
- It was a randomized-controlled trial, the gold standard of medical research, in which researchers test an intervention against a placebo.
- The study enrolled patients most likely to be at risk from severe Covid-19 disease: those over 50 with at least one additional risk factor and mild to moderate symptoms. People who had no symptoms or who had advanced disease were excluded.
- Participants were enrolled only after a PCR test confirmed Covid-19 infection.
- It was a multicenter trial conducted at 20 public hospitals and a Covid-19 quarantine center in Malaysia between May 31 and October 25, 2021.
In addition to the fact that ivermectin didn't work, people who took it had more side effects than those who didn't, and sometimes those side effects were severe, including heart attacks, anemia and diarrhea that led to shock.
"The higher incidence of side effects with ivermectin in our study raises concerns about the widespread use of this drug outside clinical trial setting," lead researcher Dr. Steven Lim told CNN in an email.
"The public should understand that the highly touted safety profile of ivermectin is related to its use as an anti-parasitic drug. The use of ivermectin as an antiviral in COVID-19 is a totally different ball game, with notable differences in dosing, duration and mechanism of actions," wrote Lim, an infectious-disease specialist at Raja Permaisuri Bainun Hospital in Perak, Malaysia.