The FAA issued a new guidance barring pilots from flying if they have taken hydroxychloroquine within the past 48 hours.

Hydroxychloroquine, an antimalarial medication that can also be used to treat rheumatoid arthritis, has been touted by President Donald Trump as a possible treatment for the novel coronavirus, or COVID-19.

However, doctors have argued that any evidence that the treatment is effective against COVID-19 is anecdotal, with no clinical trials showing efficacy. Doctors also warn of potentially serious side effects.

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The Federal Aviation Administration (FAA) will bar pilots from flying if they have taken the antimalarial drug hydroxychloroquine within the past 48 hours.

Hydroxychloroquine has been heavily touted by President Donald Trump as a possible treatment for COVID-19. The medication has not been proven effective or safe for treating the virus in clinical studies.

A spokesperson for the FAA confirmed the action in an email to Business Insider.

"As with all drugs, the FAA takes a conservative approach when evaluating how a particular substance interacts with aviation professionals and the ability to do their jobs safely," the spokesperson said. "Chloroquine and hydroxychloroquine were both reviewed by the FAA Federal Air Surgeon when they entered the market and have long been considered generally incompatible for those performing safety related aviation duties."

"Due to the wide variety of dosages and lack of standardized protocols for treating COVID-19, pilots using these medications are disqualified from performing safety related duties until 48 hours after they have stopped using them."

The new directive was first reported by CNN.

According to CNN, the original FAA guidance said that there is "no satisfactory scientific evidence that use of these medications decreases the severity of the virus."

"Exercise of social distancing and hand washing represent a far more effective means of prevention," the guidance said, according to CNN. "As information changes, we will update our policy based on the best scientific evidence available to us."

Hydroxychloroquine has been a contentious subject as the world searches for a way to mitigate the COVID-19 pandemic. Several doctors have reported anecdotal evidence that the antimalariall has helped patients with the novel coronavirus, but medical professionals have also warned of the possibility of serious and potentially life-threatening side effects, including cardiac arrhythmia.

The FAA does allow exceptions for pilots with arthritis to take small doses of the medication. Those pilots are typically required to pass an eye exam and meet other criteria in order to receive a special certification.