Brain Scientists Look Beyond Opioids To Conquer Pain

Nov 13, 2017
Originally published on November 15, 2017 6:47 am

The goal is simple: a drug that can relieve chronic pain without causing addiction.

But achieving that goal has proved difficult, says Edward Bilsky, a pharmacologist who serves as the provost and chief academic officer at Pacific Northwest University of Health Sciences in Yakima, Wash.

"We know a lot more about pain and addiction than we used to," says Bilsky, "But it's been hard to get a practical drug."

Bilsky is moderating a panel on pain, addiction and opioid abuse at the Society for Neuroscience meeting in Washington, D.C., this week.

Brain scientists have become increasingly interested in pain and addiction as opioid use has increased. About 2 million people in the U.S. now abuse opioids, according to the Centers for Disease Control and Prevention.

But at least 25 million people suffer from chronic pain, according to an analysis by the National Institutes of Health. That means they have experienced daily pain for more than three months.

The question is how to cut opioid abuse without hurting people who live with pain. And brain scientists think they are getting closer to an answer.

One approach is to find drugs that decrease pain without engaging the brain's pleasure and reward circuits the way opioids do, Bilsky says. So far, these drugs have been hampered by dangerous side effects or proved less effective than opioids at reducing pain.

But substances related to snail venom look promising, Bilsky says.

The cone snail uses its venom to paralyze fish. And scientists discovered that this venom contains substances that act as powerful painkillers. And because these substances do not affect the same brain circuits that opioids do, they have the potential to be much less addictive.

At least one drug related to snail venom is already on the market, though it's not widely used because it must be injected into the spinal column.

Another new approach to pain management involves targeting brain circuits that can amplify or dampen our perception of pain.

Scientists have known for a long time that when someone is fearful and anticipating pain – say, during a trip to the dentist – they will experience more discomfort. That's because fear and expectation circuits in the brain can amplify the pain signal coming from a tooth or some other area.

Depression and isolation can also amplify pain, Bilsky says. "If a person in pain stays home instead of going to their mahjong group, that feeds an escalation in pain," he says.

And there's evidence that chronic pain can change the brain's wiring in a way that makes a person more sensitive to any future injury.

So brain scientists are looking for ways to tweak the brain circuits that affect our perception of pain.

Already, doctors often prescribe antidepressant drugs to people with chronic pain. And researchers are trying drugs that help the brains of people with chronic pain "forget" past pain.

They are also looking for ways to erase memories of pain.

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DAVID GREENE, HOST:

This question of how to find that balance when you have patients in pain and doctors who are fearing addiction is coming up this week as the Society for Neuroscience holds its meetings here in Washington, D.C. And NPR's Jon Hamilton has been attending. And he's with us in the studio. Hi, Jon.

JON HAMILTON, BYLINE: Hi.

GREENE: So is this the future we're looking at, people who are in chronic pain - like we just heard - having to struggle to get treatment because of these legitimate fears about addiction?

HAMILTON: It's the future that doctors and scientists are trying to avoid. But here's the problem - in the U.S. right now you've got, like, 2 million people who are abusing opioids. At the same time, you've got more than 50 million people - some estimates say 100 million - who are in chronic pain. So how do you balance trying to curb drug addiction while you're still looking out for people who are in pain?

And I should say, doctors have faced this dilemma before. Back in the 1980s, there was the war on drugs, there was the Nancy Reagan Just Say No campaign, and back then, the concern was largely illicit drugs. But it had an effect on doctors, and many of them became really reluctant to prescribe addictive drugs. And there were cases where cancer patients could not get drugs to relieve their pain.

GREENE: So a lot of neuroscientists here in Washington, D.C., this week - who you'll be spending time with - are you learning anything from them?

HAMILTON: Yes, I already have learned a few things from them. Later today, of course, there's going to be a panel of scientists who are talking about precisely this topic - addiction and opioids and pain. And one of the things researchers have learned is how many different brain circuits there are involved in both addiction and pain.

You know, for example, there's now a whole lot of research showing how the brain actually creates what they would call our perception of pain. So for instance, when you stub your toe, there's a signal that goes up into your brain. But that signal - the strength of that signal - is affected by all these things - attention, emotion, your mood. And so if, like, you're at the dentist and you're expecting to feel pain, you will feel more pain. If you're depressed, you are likely to feel more pain. If you're distracted, you may feel less pain.

GREENE: So many factors.

HAMILTON: So many factors.

GREENE: Well, is there a way to use that knowledge and this reality that there are so many factors to come up with better medication for pain that maybe avoids the addiction we see in opioids?

HAMILTON: That is the hope. I was talking to a scientist named Ed Bilsky. He's from Pacific Northwest University. He's the guy who's going to be moderating the panel later today on opioids and pain. And he told me the problem with opioids is that they are this really blunt instrument for treating pain. So at the same time they're hitting these circuits that are involved in pain, they're also hitting these circuits that are involved in reward and pleasure and all the things that are related to addiction. So the idea is to come up with drugs that are much more specific.

And there are a few candidates out there, actually. One of the most interesting ones I've been hearing about is made from the venom of a type of snail.

GREENE: Huh.

HAMILTON: And what's great about it is it targets totally different receptors in the body than opioids do, and yet it appears to be much more powerful as a pain reliever. So there is reason for hope.

GREENE: NPR's Jon Hamilton. Thanks, Jon.

HAMILTON: You're welcome. Transcript provided by NPR, Copyright NPR.