Jonathan Lange’s Sept. 10 ivermectin piece requires clarification.

Some of his points are correct: (1) ivermectin is safe in doses approved for humans, and (2) it is FDA approved in humans for certain intestinal parasites. Licensed health care providers may prescribe it legally “off-label,” including for COVID-19, but this is not advisable.

Ivermectin first attracted attention when it showed some activity against various viruses (including SARS-CoV-2) in the laboratory, although at concentrations that are difficult to achieve safely in humans. Various small European studies suggested some benefit in COVID-19, but many of these studies were flawed, or too small to achieve statistical significance. One study was retracted because the authors committed plagiarism and manipulated their data.

Ivermectin is being promoted in some circles as an effective prevention or treatment for COVID-19. Some people get it from their health care provider; others buy it from agricultural outlets without a prescription, in doses meant for livestock. Some poison control centers are reporting ivermectin overdoses.

The Infectious Diseases Society of America ( is a network of more than 12,000 communicable disease specialists (physicians and other scientists). It is not a governmental organization. Its recommendation, after considering all available studies, is that current data do not support using ivermectin for COVID-19, except in the context of a well-constructed clinical trial.

Various trials are currently planned or in progress. If one or more of these shows a benefit of ivermectin, the FDA can authorize emergency use if the data are convincing enough. One large study is planned in the UK, but not yet completed.

So far, one completed study of 500 patients with COVID-19, half of whom got ivermectin, showed no benefit in preventing hospitalization. The ivermectin group actually did worse.

Even Merck (, a company that makes ivermectin, and which would profit from its sale, advises against using it to prevent or treat COVID-19.

The real danger with ivermectin is the unsupported belief that it will keep people well and out of the hospital. Vaccination, although not 100% perfect, is currently the safest and best way to achieve that goal, and it is free.

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