OTTAWA — As Canada takes part in a rapid global test of multiple drugs that might be promising for treating COVID-19, the country’s top public health official is warning not to prejudge outcomes and cautioning against the dangers of using unproven therapies. One of the best-known of these is hydroxychloroquine, also known more simply as chloroquine, a long-standing staple treatment for malaria. U.S. President Donald Trump caused a stir last week when he touted chloroquine as a possible treatment for victims of the novel coronavirus. Trump even decreed it has been approved by the Food and Drug Administration. That turned out not to be true, but it did spark interest in the drug around the world.

Former Alberta Wildrose party leader Danielle Smith pronounced a few days later on social media that a French study had found “hydroxychloroquine cures 100 per cent of coronavirus patients within six days of treatment.” Those doctors did find that the drug reduced detection of the virus in the upper respiratory tracts of patients treated with it compared to another group. But according to the Centers for Disease Control in the U.S., the study was small, not randomized, and did not look at the eventual outcomes of the patients, including deaths. The authors acknowledged that some of the people treated with chloroquine were dropped from the study because they stopped taking it, because their conditions had deteriorated. WATCH: Trump and health official differ in tone of possible drug treatment for coronavirus. Story continues below.

Smith has since apologized for the tweet, and any undue anxiety and frustration it may have caused. In the wake of these promising claims about the drug, Canadian drug company JAMP Pharma Group announced plans Monday to donate one million doses to Canadian hospitals as a treatment for COVID-19. That move sparked a stern warning from the country’s chief public health officer, Dr. Theresa Tam. “People have to be really, really careful about this. Don’t do it,” Tam said in a briefing Monday.

Adrian Wyld/THE CANADIAN PRESS Chief Public Health Officer Theresa Tam responds to a question during a news conference on the COVID-19 virus in Ottawa, March 23, 2020.

The CDC said there is no available data from randomized clinical trials to inform the use of hydroxychloroquine against the novel coronavirus. Using untested medication might not only be ineffective against COVID-19, it could also be dangerous, as all drugs come with side effects, Tam said. “We need the evidence before you can provide medication to people,” Tam said. “It is absolutely essential that you do science based treatment.” Earl Brown, an emeritus professor of virology with the University Ottawa, said the drug works by lowering the acidity inside cells, making it more difficult for the virus to get in.

People have to be really, really careful about this. Don’t do it. Dr. Theresa Tam

In a lab setting it works against several strains of virus, he said, but it hasn’t been proven for use in patients with COVID-19. He said it should be used with caution under the best circumstances. “The daily dose is around a gram, and a dangerous dose is around two grams,” he said, adding that you don’t typically want the optimal dose and the dangerous dose to be so close. “It suggests a bit more risk,” he said, which can include death. Other side effects include blurred vision, nausea, vomiting, abdominal cramps, headache, and diarrhea. Long-term use can cause vision loss. Other drugs have generally taken over from chloroquine as go-to malaria treatments.