Bruce Boise said "every day was different" even "exciting" to him as a pharmaceutical salesman at Cephalon. But that all changed in 2000 when he says he was ordered by his boss to promote drugs "off-label" to doctors -- meaning for purposes that were not approved by the Food and Drug Administration -- in order to boost sales.

"It's not legal for a pharmaceutical company to promote off-label," said Dr. Christopher Gharibo, a NYU pain specialist.

"I didn't do very well at all with selling off-label, because my heart just wasn't in it. I didn't think it was right," said Boise, who shared his story with host Alex Ferrer in the "Whistleblower" season finale, "Opioid Lollipops: The Case Against Cephalon." So, Boise took action and contacted investigators at the FDA. They wanted proof the company was breaking the law.

"A couple of agents … sat down and talked to me about what the company was doing and asked me to bring material to show how they were doing it," Boise explained.

In 2003, agents asked Boise if he'd wear a wire at a Cephalon national sales meeting.

"I thought if that's what … it took to stop a company from doing what they're doing," he told Ferrer.

Boise was outraged when he heard a sales rep describe how he was promoting Actiq, a medical lollipop made with the extremely powerful opioid fentanyl to general practitioners.

"Fentanyl," Dr. Gharibo explained, "is a very strong opioid. It's about a hundred times stronger than morphine."

Fentanyl is the drug that killed Tom Petty and Prince and, according to Gharibo, "very easy to overdose on."

The FDA had approved Actiq only for cancer patients in acute uncontrolled pain – a very small market. Cephalon, though, pursued a much larger one. "They eventually marketed it," Boise said, "for low back pain and migraine patients."

"You're talking about a Class 2 narcotic," he said. "And you're giving it to a migraine patient. … So it puts patients at risk."

Boise was fired when the company learned he was working with the FDA -- and then his fears about promoting Actiq for off-label use were realized: Robin Geist-Wick, a migraine sufferer who took Actiq to dull her headaches, tragically, became addicted.

"It hooked her right away," Robert Wick said. "I wish Robin had never taken that Actiq. I think she'd still be alive."

Peter Chatfield is Boise's whistleblower attorney.

"In light of the opioid crisis that we all know about, would it be fair to say that Bruce was the canary in the coal mine?" Ferrer asked Chatfield.

"I think with hindsight about what has happened, he absolutely was," he replied. "We had never seen anything like that. And you can see what happened -- it took off from there."

Boise did not sell Actiq himself, but he heard a Cephalon sales rep give a presentation about how he marketed Actiq to general practitioners at their national sales meeting where he wore a wire for the FDA. He also received specific information about their promoting Actiq for migraines and lower back pain from a colleague who worked directly in Actiq sales.

Boise did receive a financial reward for blowing the whistle; it was a portion of Cephalon's settlement with the government. The court awarded him $17 million. After taxes and legal fees, Boise took home $6.5 million. That was one of the largest rewards in this season's Whistleblower stories.

"Opioid Lollipops: The Case Against Cephalon" airs Friday, June 28 at 8/7c on CBS.