A powerful painkiller that's many times more potent than heroin, fentanyl is the reason music icon Prince is dead. It's also a growing problem in Canada, where fentanyl-related deaths have spiked in the past five years. Here's what you need to know about this narcotic.

When Prince passed away last month, some people wondered if the music icon had succumbed to a drug overdose. As it turns out, he did—but the drug in question was a surprise: fentanyl, a powerful painkiller often prescribed for chronic pain. (Prince had a history of hip problems and underwent hip replacement surgery in 2010.)

But this isn't the first time fentanyl has been in the news, especially in Canada. According to the Canadian Centre on Substance Abuse, there was, on average, one fentanyl-related death every three days between 2009 and 2014—and they're pretty sure that's lowballing it.

We asked Dr. David Juurlink, head of the Division of Clinical Pharmacology and Toxicology at Sunnybrook Health Sciences Centre, and Dr. Michelle Arnot, a senior lecturer in the University of Toronto's Department of Pharmacology and Toxicology, five of our biggest questions about fentanyl. Here's what they had to say.

What is fentanyl?

It's a synthetic opioid drug that is chemically very similar to heroin. It's predominantly prescribed to relieve pain, much like morphine, oxycodone and codeine. But fentanyl is much, much stronger.

"What makes fentanyl interesting is that it is about 80 to 100 times more potent than morphine," says Dr. Arnot. When patients become tolerant to painkillers, Dr. Arnot says physicians will bring in the "superhero" drug: fentanyl.

Fentanyl can elicit a euphoric feeling, which is one of the non-medical reasons why individuals seek it out. This is because the drug doesn't just decrease pain; it also reduces anxiety and activates the mesolimbic system, the part of the brain that is in charge of natural rewards such as sex and eating.

Why is it so dangerous?

One of the key reasons is its potency.

"It doesn't take very much of the stuff to cause pain relief," says Dr. Juurlink. Considering how strong a small amount of the drug is, accidentally taking just a bit more can be lethal. "It doesn't take much more of it to actually cause a person to become comatose and stop breathing."

On top of the dangers surrounding potency, there is a big issue with addiction and withdrawal when it comes to fentanyl (and opioids in general).

"Individuals can actually start taking pain medication or opioids from a purely clinical reason—they have had cancer pain, they have had back pain—but sometimes what happens, if it's not monitored or supervised correctly, is individuals become reliant, for lack of a better word, on the drug," says Dr. Arnot.

When patients try to wean themselves off, they become agitated, experience insomnia and they can even become more susceptible to pain.

Taking fentanyl can obviously be very dangerous, but Dr. Juurlink says that when taken properly and under the supervision of a clinician, it doesn't need to be this way.

"When you know what you're taking, you can act relatively safely," he says.

Unfortunately, not everybody knows what drugs they're taking. It's not uncommon for illegal drugs, like heroin or pills, to contain fentanyl, and for those who unexpectedly take the potent drug, the results are often lethal.

Where is it coming from?

It is prescribed by doctors, but sometimes fentanyl can make its way out of the hands of healthcare professionals.

"[It] is easily synthesized in a laboratory, and we are seeing more and more of it being created in bootleg fashion for sale on the streets," says Dr. Juurlink.

In recent years, the experts say that clinicians have been decreasing their opioid prescriptions, likely because of the dangers associated with the drugs. However, this has led some patients to seek other means of getting their painkillers.

Dr. Arnot says some people will even go as far as taking fentanyl from other people's used fentanyl patches.

"If you take that patch that's been used for 72 hours, there's still actually fentanyl in it. So what individuals will do is they'll take a needle and they'll suck out everything in that patch, so you can imagine there are other things like adhesives etc.," she says. "And then they'll inject it, because injecting the drug gives individuals a much faster high.”

How big a problem is it in Canada?

Fentanyl has become a huge problem in Canada. Experts have called the drug a nationwide disaster; across the country, there has been an almost 3000% increase in fentanyl-related deaths, from 29 in 2009 to 894 in 2014.

It's now the leading cause of opioid deaths in Ontario, while in British Columbia fentanyl was detected in a full third of all drug overdoses in 2015.

Who's at risk?

Many news stories about fentanyl overdoses make a point to mention the victim's middle class life. That's for good reason—many of the people who have become addicted to the drug aren't your stereotypical "junkie."

Dr. Juurlink explains there are two key groups of people who are at risk.

The first group includes the people who are taking fentanyl under their doctor's orders. Scarily, you can become dependent on fentanyl without abusing it—that is, while taking it exactly as prescribed. But the bigger risk comes from combining the medication with other drugs such as sleeping pills and alcohol, which happens a lot, says Dr. Juurlink.

The second key group of at-risk people includes those who are active drug abusers.

"People who are using heroin or pills they have bought on the street [are at risk] because they have no assurance as to what exactly is in them, and so it's quite possible that fentanyl or related chemicals could be in them in high concentration," he says. "[They have] no clue what they're actually taking.”

Prince's death has shone a light on the issue of opioids in general, and fentanyl in particular, but the problem goes way beyond Hollywood.

"Every time a celebrity dies of an opioid overdose," says Dr. Juurlink, "there are literally thousands of other people who have died who don't make the headlines, and this is a huge problem.”

A new study has found that your friendships can help relieve your pain. Learn more about it here.