“We did it intermittently in April, May and June of last year,” Varon said. “But as of July (2021), every patient that comes in goes on ivermectin.”

The Centers for Disease Control and Prevention issued a warning on Thursday about a rapid increase in ivermectin prescriptions and reports of severe illness in people who ingest the drug to treat the virus.

Ivermectin is a medication only approved by the FDA to treat certain parasitic infections, head lice or skin conditions such as rosacea. An over-the-counter version for animals treats heartworm disease. To date, there is no well-designed scientific study that shows ivermectin effectively prevents or treats COVID-19 at any stage of the illness, said Dr. Prathit Kulkarni, assistant professor of medicine in infectious diseases at Baylor College of Medicine.

Taking the drug for an unapproved use can be dangerous, according to the FDA. Large doses can cause a number of side effects, including nausea, seizures and death. Even levels of ivermectin for approved uses can interact with other medications, like blood-thinners, the FDA says.

In one recent case, an adult became disoriented and needed to be hospitalized after taking ivermectin tablets of unknown strength purchased on the internet, according to the CDC. Another person was hospitalized for nine days after drinking an injectable version of ivermectin intended for use in cattle. They showed up to the hospital with confusion, drowsiness, visual hallucinations, tachypnea and tremors, the CDC said.

Varon said he is using the drug in small doses “because it makes a difference” in COVID patients. He said no one has overdosed or died in the hospital after ingesting it.

“More importantly, my love for (ivermectin) is based on my personal use and good outcomes my patients have had,” Varon said in an email. “Once you see it work, it is difficult to deny its usefulness.”

Varon shared a PowerPoint presentation with the Chronicle that points to research showing some benefits in the use of ivermectin against COVID. A portion of the research came from a paper that was removed from its publication site because of concerns over plagiarism and misuse of data.

Varon referred to Dr. Paul Marik, professor of internal medicine at East Virgnia Medical School, as another proponent for ivermectin treatment in COVID patients. In a phone interview, Marik said a number of trials have shown that ivermectin works as a COVID treatment. He claimed that public health entities are steering people away from the drug because “nobody is making money from it.”

In fact, trials that suggest possible benefits from ivermectin “were deeply flawed and likely reflected biases,” said Dr. A. Clinton White, professor of infectious disease at University of Texas Medical Branch.

“By contrast, there was no effect on viral load and a trend towards a longer time of hospitalization,” White said.

Dr. Luis Ostrosky, chief of infectious diseases with McGovern Medical School at UTHealth Houston, said early studies only showed the benefits of ivermectin when used in quantities that could be harmful to humans.

He said patients who recover after ingesting ivermectin should not be used as proof that the drug neutralizes the virus. The vast majority of hospitalized patients will improve, regardless of treatment, he said.

“It’s very challenging to study medication in that setting, where there’s a high proportion of patients who are going to be getting better no matter what,” he said.

Varon has been heavily featured in both local and national media for working hundreds of consecutive days treating COVID patients. Multiple outlets referred to him as the “Covid Hunter.”

He previously used hydroxychloroquine to treat COVID patients but has since stopped the practice, he said. Studies have shown that drug causes serious heart rhythm problems and other safety issues when used to treat the virus.

Varon said he also uses fluvoxamine, which is designed to treat obsessive-compulsive disorder and depression, for COVID patients who end up in the ICU. That drug also is not FDA-approved for the treatment of any infection.

The Texas Medical Board said the off-label use of drugs as an alternative therapy for COVID-19 patients “is completely permissible.”

“As is the case with any alternative therapy, physicians must ensure they comply with Board Rule 200 which requires physicians to provide full disclosure of treatment options, side effects and obtain informed consent,” the medical board said in a statement.

julian.gill@chron.com