National security adviser: Trump works '18 hours a day' while taking hydroxychloroquine

White House National Security Adviser Robert O'Brien claimed this week that President Donald Trump works up to 18 hours a day while taking hydroxychloroquine.

During an interview on CBS, host Margaret Brennan asked O'Brien if Trump had created a national security risk by taking the unproven drug despite having a heart condition.

"Is there a national security risk for the commander-in-chief to be taking a medication that the FDA warns the public that there is risk of having heart problem?" Brennan asked.

O'Brien insisted that Trump is taking the drug "in close consultation with his physician."

"I think the president is under great medical care," O'Brien said. "And I think he's doing the right thing that he and his physician believe is good for the president."

"I'm not concerned about his health," he added. "The guy has got more energy than anyone I've ever seen. He works 16, 18 hours a day. So I don't see any change in his strong performance as a result of whatever health regiment he's under."

Watch the video below from CBS.