The Centers for Disease Control and Prevention sent out an advisory on Thursday against the use of a drug prescribed to fight parasites in animals, which some believe can also treat those diagnosed with COVID-19. The CDC said it is seeing an alarming number of prescriptions for the drug ivermectin, due to false claims that it can be used to treat COVID-19. Ivermectin is primarily used by veterinarians to deworm large animals like horses and cows, and can be used for lice or parasites in humans. The US Food and Drug Administration had previously cautioned against using ivermectin to treat Covid-19, tweeting over the weekend: “You are not a horse. You are not a cow. Seriously, y’all. Stop it.”

Doctors investigated the possibility of using the anti-parasitic drug to fight COVID, but clinical trials yielded insufficient evidence. The use of Ivermectin is now prompting a huge increase in calls to poison control centers and visits to understaffed emergency rooms and overdoses of the drug can cause stomach problems, nerve damage, seizures, disorientation, coma and even death.

The CDC advisory reiterated 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.