They are all around us, a secret society of the successful. They say what gives them an advantage, though, isn't just purposefulness or perseverance but a little secret weapon, a pill called Provigil.

There is the lobbyist, who wakes up at 5 a.m. to complete two full workouts before heading to work.

"I could not do this without Provigil. You know, it just wouldn't be the same," she told ABC News, asking that ABC News not identify her. "It's amazing. ... I just don't get ... why more people don't know about it."

John Withers, a computer programmer, can write code for 12 hours at a time.

"It helps you focus up for exceptionally long periods of time," he said.

And then there is the brain researcher who can find connections no one else is seeing. She asked that we not name her.

"It's just a clear day," she said. "The fog isn't there."

Provigil is approved only for narcolepsy, sleep apnea or for people who work irregular hours, but hidden among those who take it are pockets of healthy Americans taking it just to boost energy and enhance focus. It excites the mind so much that Provigil has been nicknamed "Viagra for the brain."

Prescription sales for this class of drugs has increased by 73 percent in four years, from $832,687,000 in 2007 to $1,440,160,000 in 2011, according to IMS Health.

Online there are hundreds of sites evangelizing for Provigil that explain how to get a doctor to write a prescription or how to get the drug without one.

Many Provigil users are secretive, but not Dave Asprey, a successful executive of a billion-dollar Internet security firm who often starts his day at 4:45 a.m. by popping a pill.
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"[It] can be the difference between I'm just making it through the day to I had the best day of my life," Asprey told ABC News.

Asprey says he once flew 20 hours to Australia with almost no sleep, got off the plane, took Provigil and delivered a series of speeches that were so good they made the local papers.

As a kind of an experiment ABC News asked Asprey to stop taking the drug for three days. Off the drug, he said he felt off.

"I've noticed that my speech is very slightly altered," he said.

After three days, Asprey popped a Provigil and he says it took only 17 minutes for him to snap back. He said the world suddenly seemed brighter.

Asprey compared it to the scene in "The Wizard of Oz" where everything goes from black and white to color.

ABC News had Asprey take some cognitive tests, and there was a pronounced improvement over the day before when he was not on Provigil.

So, should we all be on Provigil?

Doctors warn that you are really rolling the dice with this drug. There have been no long-term studies of Provigil and its effects on healthy brains have never been studied. Doctors also warn that possible side effects include sleep deprivation and potentially lethal rashes and worse.

Provigil is a wake-promoting agent, but doctors admit they don't really know how it works.

"Provigil is not a substitute for sleep. Sleep deprivation can cause and worsen heart disease, diabetes and high blood pressure," said Dr. Joanne Getsy, chief of the Sleep Medicine Section at the Drexel University College of Medicine in Philadelphia.

And there have been no studies proving that performance actually improves with Provigil. "Sleep deprivation can actually worsen performance," said Getsy.

"It's very tempting, but I think long-term it's a bad idea," said Dr. Martha Farah, a cognitive neuroscientist at the University of Pennsylvania. "We actually know very little about the long term effects."

Astonishingly, Asprey says even if it were to turn out that Provigil could shorten his life he wouldn't give it up and neither would the lobbyist or brain researcher who take it. They told ABC News they aren't worried and aren't about to stop using Provigil.

"I would like to really live during those years when I'm alive. I'd like to be fully alert, fully focused, and fully present all the time" Asprey said. "Provigil helps me do that."