When Hillary Clinton was Secretary of State, she had her staff conduct research on Provigil, a drug used to treat sleepiness and off-label for Parkinson’s disease, according to a declassified State Department email released by WikiLeaks.

The drug — Provigil — is a controlled substance approved by the U.S. Food and Drug Administration for the treatment of narcolepsy and other conditions that cause daytime sleepiness.

It is also used off-label to treat excessive sleepiness in people with Parkinson’s, multiple sclerosis, and Alzheimer’s disease, as well as other disorders.

In an email sent on Oct. 24, 2011, State Department staffer Jake Sullivan sent Clinton information about Provigil, including side effects of the drug used to stay awake for long periods of time, in an apparent response to her request for information, according to the WikiLeaks post.

“Provigil is used to treat excessive sleepiness caused by narcolepsy or shift work sleep disorder (sleepiness during scheduled waking hours among people who work at night or on rotating shifts),” Sullivan wrote.

“It is also often prescribed to treat excessive sleepiness in patients with Parkinson's, Alzheimer's, and multiple sclerosis. Additionally, it has also gained a following among students, truckers, and others who want to stay awake for extended periods of time.”

Provigil (modafinil) was developed by the French firm Lafon and approved by the FDA for narcolepsy in 1998. It is now sold under by the Pennsylvania drugmaker Cephalon.

It is unclear from the email why Clinton might have asked for information about the drug. But Sullivan noted there is “military interest” in its use.

“In the U.S. military, modafinil has been approved for use on certain Air Force missions,” he wrote. “The French, British, and Indian militaries have all expressed interest in modafinil.”

Provigil has also gained popularity as a “smart drug,” particularly in Europe, because of its ability to boost alertness.

Modafinil has been called the “world's first safe smart drug” by researchers at Harvard and Oxford universities who suggested its effects were “low risk” when taken in the short term.

Clinton has been the target of numerous rumors she is in failing health, most recently due to coughing spells she suffered.