Post-Surgical Pain: At the Boundaries of Pain and Addiction

Post-Surgical Pain: At the Boundaries of Pain and Addiction

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Dr. Hance Clarke
Assistant Professor
Director of Pain Services
Director of Transitional Pain Service
Medical Director of Pain Research Unit
Medical Director of Ehlers-Danlos Syndrome Program
Department of Anesthesia, University of Toronto

By: Alexa Desimone
Photo By: Krystal Jacques

More than 230 million people worldwide undergo a surgical procedure each year.1 Commonly, patients experience moderate to severe acute post-surgical pain, which dissipates within three to six months. However, as many as half of patients can develop chronic post-surgical pain (CPSP). Due to the persistent and debilitating nature of this pain, these patients are at a greater risk of persistent opioid use one year after surgery.2 Though fraught with side effects and addictive potential, opioids are still the most effective medication for acute pain, making them useful for patients after surgery. Unfortunately, an increasing number of CPSP patients remain on long-term, high-dose prescription opioids with limited knowledge and assistance on how and when to taper off.

In Ontario, about half of surgical patients are discharged with an opioid prescription.3 When patients suffering from chronic pain after surgery stringently take their required dose of an opiate to mitigate their symptoms, their bodies eventually develop a tolerance to the drug. Inevitably, they express to their physicians that their pain is still impeding daily-living, and their dose increases, starting a repeating cycle. Thankfully, this is a relatively rare occurrence, seen in about 15% of CPSP patients (which is only a small subset of the 50% of patients who go on to develop CPSP).3 Furthermore, patients who are opioid-naïve, meaning they have never taken an opiate in the past, have less than a 3% risk of persistent opioid use six months after surgery, and less than 1% after one year.4 Nevertheless, the subset of the population that do continue to rely on opioids can be very challenging to treat and can experience significant decreases in their quality of life if their pain is not appropriately managed.

In the past, pain scientists looked at pain and addiction as separate entities. The pain that leads to the opiate consumption is all but forgotten when pain and addiction are separated. However, Dr. Hance Clarke, Director of Pain Services and Medical Director of the Pain Research Unit at Toronto General Hospital (TGH), was one of the key opinion leaders in Canada to challenge that ideology. He believes pain and addiction do coexist in some patients. People may develop an opioid use disorder even though the medication was intended for their pain—and both the pain and addiction need to be treated in tandem.

Dr. Clarke completed his PhD through the Royal College Clinical Investigator Program at the Institute of Medical Science, and is currently an assistant professor in the Department of Anesthesia at the University of Toronto. As an anesthesiologist, Dr. Clarke appreciates the ability to take a more interventional approach with patients. Indeed, pain management incorporates a number of specialists including neurologists, family physicians, rheumatologists, physiatrists, and more. Thus, during the time of his PhD, Dr. Clarke had opportunities to connect and network with people from many different fields. This allowed him to appreciate the value and expertise that different fields bring to pain management.

In 2014, a multidisciplinary pain program called the Transitional Pain Service (TPS) was developed at TGH to identify patients at risk of CPSP and provide a holistic approach to pain management.1 As the current director of the TPS program, Dr. Clarke understands the need to incorporate various interventions, including psychological, medical, pharmacological, and physical therapies, in order to prevent and treat factors that increase the risk of CSPS and opioid misuse. The TPS targets high risk patients, such as patients with a history of chronic pain, drug or opioid misuse, as well as those with significant psychological co-morbidities. When admitted to the program, patients are seen every two weeks. Their opioid or other analgesic medications are adjusted with the goal of optimizing their daily function. Additionally, these patients receive psychological treatments (e.g. Acceptance and Commitment Therapy), alternative medicine treatments (e.g. acupuncture), and physiotherapy to assist in restoring function and to help them better cope with their pain.5 Overall, the TPS aims to break the cycle of chronic pain treatment that can lead to chronic opioid misuse and addiction.

For Dr. Clarke, it is the individual victories that keep him going. When patients on high dose opioids start to understand that they also have a misuse issue, the ability to introduce other coping strategies and even change the course of their lives becomes possible. This potential is what motivates Dr. Clarke. “We’re all just human beings and the moments in your life which enable you to change an individuals’ trajectory in a meaningful way, well, that’s what keeps me going,” said Dr. Clarke.

Working in the midst of the current opioid crisis, Dr. Clarke is keenly aware of the importance of the work that he is doing. “[We] really have an opportunity to help direct change, but we need to make sure we direct change with good science and evidence,” explained Dr. Clarke. He certainly is not someone who wants to stop the use of opioids. He explains that not all deaths from overdose start with the prescription pad. As with many public health officials, he is deeply concerned about the supply of illicit fentanyl, an opioid 100 times stronger than morphine, being mixed in with street drugs. In the pain world, he knows that if we are going to start cutting down on opioid use, we must embrace other methods of pain control – a goal which his TPS clinic is striving towards.

In the future, Dr. Clarke is most excited to begin looking at the effects of cannabis on pain. With the new legalization of cannabis in Canada, we have greater ability to investigate its potential therapeutic effects. Dr. Clarke’s current projects surrounding cannabis aim to investigate publicly available products and test what active ingredients are in those products. He has observed 10-90% variability between these products, yet individuals are paying the same amount of money for two completely different products leading to differing effects. “This is an industry that has yet to be medically driven and has been lead by a venture capitalist industry, it is time that science starts to lead the Canadian population” Dr. Clarke remarks. However, he believes that in 5-10 years, a rigorous medical cannabis industry will evolve and patients will have products available with good science and randomized control trials to ensure the public’s confidence in the effects the product is reported to have.

There are still many unanswered questions regarding pain and opioid use disorder, however, Dr. Clarke is eager to pursue his research into medical cannabis and pain. At the same time, he and the TPS team are busy working to tackle addiction from a novel angle – hopefully before it even develops.


  1. Katz, J., Weinrib, A., Fashler, S. R., et al. (2015). The Toronto General Hospital Transitional Pain Service: development and implementation of a multidisciplinary program to prevent chronic postsurgical pain. Journal of Pain Research, 8, 695-702.
  2. Clarke, H. (2016). Transitional Pain Medicine: novel pharmacological treatments for the management of moderate to severe postsurgical pain. Expert Review of Clinical Pharmacology, 9(3), 345-349.
  3. Huang, A., Azam, A., Segal, S., et al. (2016). Chronic post-surgical pain and persistent opioid use following surgery: the need for a transitional pain service. Pain Management, 6(5), 435-443.
  4. Clarke, H., Soneji, N., Ko, D. T., et al. (2014). Rates and risk factors for prolonged opioid use after major surgery: population based cohort study. British Medical Journal, 348.
  5. Weinrib, A. Z., Azam, M. A., Birnie, K. A., et al. (2017). The psychology of chronic post-surgical pain: new frontiers in risk factor identification, prevention and management. British Journal of Pain, 11(4), 169-177.