Early in the COVID-19 crisis, doctors desperate for an answer to the virus began reviewing whether any drugs already available could be used as effective treatment. Ivermectin, an anti-parasitic, was administered to some patients across the globe with seemingly positive effects. However, some health officials have challenged the effectiveness of the drug to treat COVID-19. On one side, there are doctors who say ivermectin can help end the pandemic if used globally. On the other are public health officials who have reviewed the data and say the drug’s effectiveness against COVID-19 isn’t conclusive. Ivermectin works by altering cellular channels, CNET reports. The drug inhibits some viruses from infecting cells, thus preventing the virus from spreading. Ivermectin is usually given to treat parasitic infections such as lice and Strongyloides. Scientists at pharmaceuticals giant Merck discovered ivermectin in 1975 and began to use it to treat scabies, river blindness, and other parasitic diseases carried by worms and lice starting in 1981. It’s on the World Health Organization’s list of essential medicines for a basic health care system. More than 250 million people take the drug across the globe each year, and it’s effective for animals as well. The drug is considered safe when taken in appropriate dosages. Side effects for ivermectin vary depending on whether it’s taken orally to treat intestinal infections or topically for skin infections. Oral tablets can cause drowsiness, nausea, vomiting, and, in very rare cases, an increase in heart rate and seizures. Side effects for the topical ivermectin can include skin rash and irritation, while dry skin and stinging pain are severe and rare. This is where things get complicated. Public health agencies, including the U.S. Federal Drug Administration, the National Institutes of Health and the World Health Organization, don’t suggest ivermectin’s use to treat COVID-19. They cite the lack of data from large, randomized trials confirming the drug’s effectiveness to treat the disease. Some doctors who cited multiple smaller studies and firsthand experience claim ivermectin indeed works to prevent people from developing symptoms from COVID-19 and can shorten recovery time for those infected.