Letter to the Editor: A biologist’s perspective to add to the ivermectin debate

Bruce Menzel

Ivermectin is primarily used as an antiparasitic agent for humans and other mammals. Its action is to interfere with important intracellular processes of protein transport in target parasites. For this purpose, it is approved for specific human applications by the World Health Organization and the U.S. Food and Drug Administration.

There are proposals for repurposing the drug as a first-line defense against COVID-19. Some countries have adopted this position already but not the U.S. because of insufficient clinical studies on its efficacy for that purpose.

Descriptions of 214 mostly small-scale doctor-initiated investigations from around the world are registered at, however, results and conclusions are not given.

A single ongoing American large-scale trial testing ivermectin efficacy and two other proposed repurposed drugs is also listed under study NCT04885530. Zaidi and Mobaraki, who published their study in 2021 in the Journal of Antibiotics’s Volume 75, have extensively reviewed current knowledge on ivermectin’s action on the SARS-CoV-2 virus. Their cited studies, while important for improving understanding of ivermectin activities, have been primarily laboratory in-vitro analyses.

Their conclusion is that “… it is still unclear if any of these activities will play a role in the prevention and treatment” of COVID-19 disease.” They believe that more controlled large-scale clinical trials are needed to translate current knowledge into useful treatment.

Philip Huff’ is correct in citing such a study, conducted in Brazil, as a rare example of the needed additional research. Its authors concluded that ivermectin is ineffective in the treatment of COVID-19.

As the results of future clinical trials become available, public health agencies will critically evaluate and compare them to make decisions upon which to base their recommendations for any additional ivermectin applications.


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