(CNN/WSVN) — The US Centers for Disease Control and Prevention has sent a health advisory warning doctors and the public about the “rapid increase” in prescriptions for the anti-parasitic drug ivermectin.

The CDC also cautions about an increase in reports of severe illness caused by the drug to poison centers.

Ivermectin is used to treat parasites such as worms and lice in humans and it is also used by veterinarians to de-worm large animals.

Normally, about 3,600 prescriptions are written for ivermectin in a week, the CDC said. This rose more than tenfold by the week of January 8, when 39,000 prescriptions were written. “Since early July 2021, outpatient ivermectin dispensing has again begun to rapidly increase, reaching more than 88,000 prescriptions in the week ending August 13, 2021. This represents a 24-fold increase from the pre-pandemic baseline,” the CDC said.

GoodRx a company that tracks drug prices has seen a similar sharp increase in prescriptions filled for ivermectin. From the company’s data for August, so far they’ve seen 20 times the average level of fills in 2019.

The US Food and Drug Administration has cautioned people against using ivermectin to treat Covid-19. Last Saturday the FDA tweeted: “You are not a horse. You are not a cow. Seriously, y’all. Stop it.”

Calls to poison control centers have increased three-fold, compared to the number of calls about the drug before the pandemic, the CDC said.

According to Florida Poison Control, they have received calls about the drug throughout the state, including in South Florida. Over 30 people have been treated in August compared to the usual one to two calls per week, officials said.

The increase in the drug’s use has impacted Florida farmers, as people head to feed stores to buy animal doses of the drug.

“This is a product that is supposed to be used for animals,” Florida Agriculture Commissioner Nikki Fried said. “There has been a significant increase on the poison control lines on this issue. People getting sick, people going to the hospital and trying to figure out what to do, so again, please talk to your medical professionals, talk to your doctors. Do not self medicate.”

Some examples of these calls included an adult who wanted to prevent Covid-19 and had to be hospitalized for nine days after drinking a cattle formula. Another person who bought pills online to treat their Covid-19 infection was hospitalized after taking five tablets a day for five days.

The CDC reminded doctors that ivermectin is not authorized or approved for use in Covid-19 patients. Doctors did investigate the possibility, but clinical trials of the drug “yielded insufficient evidence” to treat Covid-19. Scientists would need to perform more clinical trials to see if it actually worked to treat the disease. Overdoses of the drug can cause stomach problems, nerve damage, seizures, disorientation, coma and death.

The CDC advisory reminded the public that vaccination rather than treatment “is the safest and most effective way to prevent getting sick and protect against severe disease and death” from Covid-19.

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