NASHVILLE, Tenn. — Four years ago, Tennessee became the first state to allow adults to buy the antiparasitic drug ivermectin from a pharmacy without first seeing a doctor. Pharmacies can use a pre-written, blanket prescription to sell to just about anyone who walks through their doors.

The drug is now marketed and sold across the state in roadside shops and small-town strip malls with little oversight from health authorities. Highway billboards advertise ivermectin as “Available Without a Prescription in Tennessee!” while dozens of pharmacies offer highly concentrated pills, sometimes at 10 or 20 times the potency of a standard tablet.

Ivermectin is a Nobel Prize-winning, generally safe drug approved by the FDA for treating parasitic diseases in humans, which can generally be done with a single dose of three or four prescription-strength tablets. It is also used as a dewormer for horses and other livestock.

Its popularity surged during the pandemic as fringe doctors and anti-vaccine activists promoted it as a treatment for Covid. Clinical trials have shown that ivermectin is not effective against Covid.

Nonetheless, it has since become a symbol of resistance against the medical establishment among conservatives and followers of the Make America Healthy Again movement, championed by Health and Human Services Secretary Robert F. Kennedy Jr.