Quirks & Quarks

The puzzle of pain: Opioids are killing some, but saving others

We all know it when we feel it, but pain is incredibly challenging to understand and treat.
Doctors are still trying to understand the complexities of how we feel pain, which can make it hard to treat. (Simon James)

Last week the Canadian Medical Association issued new guidelines for the use of painkilling opioid drugs: "In the battle against opioid addiction, doctors are being told to 'put down the prescription pad' The powerful drugs should be used only for chronic pain, primarily for cancer, and then gradually wean patients off of them."

The guidelines are, at least in part, an attempt deal with a raging public health crisis. In 2015, an estimated 2,000 people died of opioid overdoses, some from illegal street drugs like heroin, but many from prescription drugs like fentanyl and OxyContin — often illicitly obtained.

Two scientists help us get a better understanding of the puzzle that is pain. 

Dr. Jeffrey Mogil is professor in the Department of Psychology and Canada Research Chair in the Genetics of Pain at McGill University in Montreal. 

Dr. Mary Lynch is a professor the Department of Anesthesia, Pain Management & Perioperative Medicine at Dalhousie University in Halifax.

The following interviews have been condensed for clarity and length. 

Bob McDonald: Why is it so hard then to measure a person's pain?

Dr. Jeff Mogil: I think the problem ultimately is that it's completely subjective. It's sort of intrinsically internal to the person. There are energies in the environment - there's pressure, heat, and inflammation, but they don't correlate very well at all with the experience, the perception, that people have of pain.

BM: And pain comes in different forms... you can have a needle prick at the end of your finger, but you could also have something like back pain or something really serious.

JM: Exactly, you can split pain into any number of different categories. When you do so, the biological basis completely changes. So there's no heat pain versus mechanical pain. And they're short lasting pain compared to long lasting pain. And there's pain to the skin, muscle, joints, or even to the the visceral organs. And there's pretty good evidence that all of these things are very very different.

BM: Why does there seem to be such a variability between the way people report pain? Somebody might complain a lot about some little thing and other people seem to be able to put up with a lot of pain…

JM: Yeah, this is something that I've been studying practically my whole career. They've done twin studies. I can tell you that almost half the answer is genes. And a little bit more than half the answer are other environmental factors - probably the most important, of which, is how much pain experience have you had in your life before that. And so we're trying to tease this apart but frankly I don't think we're anywhere close yet. There's a study of 500 people from Bethesda, Maryland where they were all given the exact same thermal stimulus to their forearm and were then asked to rate that on a scale from 0 to 100. There were few people at the low end that said that was about a four or five out of 100. And then there were people at the high end that said it was a 95 or 96 of a 100 and every rating in between. So as much variability as you can imagine we can demonstrate.


BM: You mentioned the genetics of pain. How is that influencing how we experience it?

JM: Well on the one hand, it's a large part of the answer. We know there are genes that influence pain sensitivity and susceptibility to developing chronic pain disorders, and how well people respond to analgesics including opioids like morphine. The problem is that when we started searching for these genes, we thought we were looking for three or five or maybe 12. Now we have reason to believe that there are probably hundreds or thousands.

BM: So you're saying that some people are actually more sensitive to pain than others because of their genetics?

JM: Oh 100 per cent. It's just that I can't tell you which genes.

BM: You also mentioned the experience with pain. How does that come into it?

JM: Yeah it turns out that one of the biggest risk factors for chronic pain and how long it's going to last and how big a problem you're going to have with it, is whether you've ever had pain before. Why that is, no one really knows. The system is probably sensitized. Each time you have an injury or some sort of insult that causes pain, it appears to make things a little bit worse than it was before.

Dr. Mary Lynch says opioids still have an important role to play in treating complex, chronic pain, which she says needs a full interdisciplinary approach involving a physicians, nurses, psychologists, physiotherapists, occupational therapists. Even then, she says opioids are definitely not her first line of treatment.

Bob McDonald: So at what point do you decide to treat a patient with opioids?

Dr. Mary Lynch: Generally when the patient's quality of life is compromised and when the pain levels are intolerable - where they're still suffering from quite severe levels of pain that they can't tolerate.

BM: So in your experience what is the likelihood that some of those patients, who are taking the opioids, will develop long-term addiction to them?

ML: The likelihood is quite low. Generally when we're introducing an opioid, we do a screen to identify those who are at risk. We try not to use them with people that have risk factors of substance use at the time. And then if there are other risk factors, we again emphasize the non-opioid strategies. But even in situations where people have, for example, a recent history or an active history of substance dependency, if there is a severe pain condition - even in that situation - it is sometimes appropriate to use the opioid, as long as you put appropriate support and structure around that person to try and minimize their risk of experiencing recurrence or running into trouble with the addiction.

Opioid pills are shown in this undated handout photo. Updated opioid-prescribing guidelines released Monday encourage doctors to avoid giving the powerful narcotics as a first-line treatment to patients with chronic, non-cancer pain. (THE CANADIAN PRESS)

BM: So then, in your mind, what is the connection between the prescription of opioids for pain and addiction, illegal drugs, and even overdoses and death?

ML: The opioids do not create the addict. The medical use of opioids is not what leads to addiction. The connection is primarily that opioids are one of the drugs that people who are at risk of addiction or who are misusing their drugs would choose in order to get high. It's really important to know that the drug does not make the addict. There are a number of big studies now that have identified that medical exposure in general populations of people who undergo surgery, for example, or who have had trauma and then require surgery, how many people in those populations - and these are studies looking at thousands of patients - are still using an opioid a year later. About 0.4 - 0.9 per cent, so less than one per cent of people go on to continue with that opioid.

BM: What you think this change in federal guidelines could lead to, if doctors are told and like pull back on your opioid prescriptions?

ML: Well it is already leading to collateral damage to those that are using their opioids appropriately for medical reasons. So we already know that people who are using opioids, under the care of their physicians, are getting less access to those opioids. Their physicians are frightened to prescribe. We have many physicians that have walked away from opioid prescribing completely because they're afraid of having their licenses taken away. We've got patients who, because they are unable to access the medications that have helped them, are at higher risk of suicide. In my own practice, I've had two of my patients commit suicide in this past year alone. Whereas in my previous 25 years of practice, I had only one patient who had committed suicide that I was aware of. The other issue is that patients who are suffering from serious pain, who have benefited from an opioid, and now can no longer get access to that opioid, may be at risk of going to the street to get that opioid. Problem is with that, the opioids that are on the street right now, the illicit fentanyl and the illicit drugs, put them at risk of overdose and death.

BM: So how then do you think we should address the complex challenges of treating pain in Canada?

ML: We have previously argued very strongly for a national pain strategy that will address all of these issues. First of all, we need to educate healthcare professionals and the general public, so that we have a fleet of well-educated healthcare professionals in the communities even in the rural communities. And then we've also got to have access tertiary care pain clinics, where necessary, to treat complex chronic pain.