The U.S. Food and Drug Administration (FDA) sent a strong directive to the public warning that a form of the antiparasitic drug ivermectin, intended for animals, should not be used in humans, including for treating COVID-19.

The letter, dated April 10, was written by Dr. Steven Solomon, the director of the FDA’s Center for Veterinary Medicine, who said that preliminary studies conducted in a petri  dish showed that SARS-CoV-2, the virus that causes COVID-19, responded to the drug.

Solomon said the FDA had yet to determine Ivermectin is “safe and effective” in humans to prevent or treat the disease.

According to the FDA, ivermectin tablets are approved to treat parasitic worms in people. Also the drug can be applied topically to treat external parasites such as head lice or to soothe skin conditions such as rosacea.

 “People should never take animal drugs, as the FDA has only evaluated their safety and effectiveness in the particular animal species for which they are labeled,” wrote Solomon. “These animal drugs can cause serious harm in people.”

While the FDA made clear it has not approved the use of ivermectin for Covid-19, it has not stopped doctors from prescribing it for parasites.

Researchers in Australia were the first to discover that a single dose of ivermectin could kill COVID-19 in a petri dish in 48 hours, according to Newsmax.

The head researcher, David Jans, Ph.D., a professor of biochemistry and molecular biology at Monash University in Melbourne, said, “It is important to stress that no none should try to self-medicate with versions of ivermectin that are for veterinary purpose or head lice.”

In a separate statement, the FDA reiterated its warning not to take ivermectin to treat COVID-19 and said some of the serious side effects of human  consumption could include skin rash, nausea, vomiting, diarrhea, stomach pain, adverse neurological events such as seizures, sudden drop in blood pressure and hepatitis. The FDA stated that it has “established a cross-agency task force dedicated to closely monitoring fraudulent COVID-19 products. We have reached out to retailers to ask for their help in monitoring these products,” according to the statement.

Solomon said in the FDA letter, “Additional testing is needed to determine whether ivermectin might be safe or effective to prevent or treat coronavirus or COVID-19.”

Several clinical trials have been approved to see if the drug is effective alone or in combination with other drugs in dealing with the virus.