In regard to the article “COVID-19 and Argumentum ad ignorantiam, or ‘not everything goes’”,1 I would like to make a few considerations.

Ivermectin has shown preclinical evidence of its efficacy against different types of virus, including SARS-CoV-2. Likewise, some authors suggest clinical evidence of the possible efficacy of the medication against COVID-19.

In a retrospective cohort study on 280 patients, Rajter et al.2 showed a significant reduction in the overall mortality rate in the group that received ivermectin (15% vs. 25.2%; OR 0.52 [CI 95% 0.29−0.96], p = .03). In the regression analysis adjusted for confounding variables, the reduction in mortality remained significant (OR 0.27 [CI 95% 0.09−0.85], p = .03; HR 0.37 [CI 95% 0.19−0.71], p = .03). Notable methodological elements in that publication include the adjustment for multiple confounding factors, including sociodemographic variables, comorbidities, the severity of pulmonary compromise, and the use of hydroxychloroquine and azithromycin.2

The dose of ivermectin is calculated in micrograms/kilogram and not in milligrams/kilogram. Thus, even though concerns regarding the effective dose for SARS-CoV-2 have been raised, the study by Rajter et al.2 showed the efficacy of the medication at a dose of 200 micrograms/kilogram, a dose that has been demonstrated to be safe. The widespread use of ivermectin that allowed for eradicating onchocerciasis as well as its use in treating parasitosis for more than 40 years provides evidence of a sufficiently safe pharmacological profile when it is used at a dose of 150–200 micrograms/kilogram.3

Though it is true that conclusive evidence is needed on the efficacy of the medication against COVID-19, to date (May 24, 2020), 14 ongoing investigations evaluating the possible efficacy of ivermectin are registered in ClinicalTrials.gov database. In this sense, its potential use outside the context of a clinical trial or research protocol for off-label medications that evaluate its efficacy and safety cannot be ruled out.4