Shifting to ‘mechanism-based’ pain treatment is way forward

Experts want a more sophisticated approach to managing chronic pain. But this is a challenge for a condition that is still not well understood, writes Gary Finnegan

The move during the past decade to recognise chronic pain as a disease in its own right has added momentum to anaesthetists’ efforts to have pain taken seriously. No longer is pain simply a symptom of an underlying injury – it’s a complex condition that needs to be addressed.
The barriers to a more nuanced approach to pain management are now coming into sharp focus. For one thing, chronic pain is still a relatively young disease. Settling on a common definition is fraught with difficulty and designing treatment strategies based on the underlying mechanism behind the pain is tricky when dealing with such a complex and subjective problem.
Add to that the fact that most pain patients are treated in the community by their general practitioner. Naturally, there is a lag time from the evolution of cutting-edge specialist knowledge to its incorporation into a typical GP exam. The degree of frustration some pain experts feel is found in many fast-moving disease areas, but family doctors would be justified in expecting clearer guidance and more user-friendly pain assessment tools.
Vicious circle of pain treatment
Prof Bart Morlion, Anaes-thesiologist Director at the University Hospitals Leuven in Belgium, warns that inadequate management of chronic pain not only hurts patients but also burdens employers and social security systems. Speaking at a media briefing in Aachen, hosted by Grünenthal, he said two thirds of patients taking prescription medications reported that their pain was inadequately controlled at times.
“In pharmacological treatment, the difficulty lies in finding the right balance between appropriate pain relief and acceptable tolerability, which can otherwise result in a vicious circle,” said Prof Morlion.
It’s a familiar tale: where low-dose analgesics fail to control pain, the dose is often increased. This may be effective, but the price can be an increased risk of side-effects. With tolerability becoming unacceptable, the dose that provided effective analgesia is reduced again – and the patient is back to square one.
The personal and social cost of this cycle is high, according to Prof Morlion. European patient surveys have revealed startling figures on the impact chronic pain can have on quality of life. A European Commission study suggested one in four people suffer chronic pain, while a separate report found that more than half of all pain patients complained of sleep disruption.
Patients’ capacity to exercise, socialise and work outside the home is also deeply affected. People with severe pain visit healthcare providers (usually GPs) twice as often and are hospitalised three times as frequently as the general population. They also miss 20 per cent more days of work than average and report lower levels of productivity.
“Absenteeism is a serious problem for patients with chronic pain – but so is ‘presenteeism’, where an employee goes to work with reduced activity,” Prof Morlion said. “If pain management is insufficient, the individual and socioeconomic burden is immense.”
Chronic pain accounts for nearly 500 million lost working days every year, at a total cost of around €34 billion. So what can be done?
Measuring pain
Acknowledging the extent of the problem is all well and good, but assessing pain accurately remains the key to taking effective action. A thorough patient history should attempt to evaluate the type of pain, its intensity, location, onset, and duration, as well as factors that ease or exacerbate severity. X-rays, computer tomography and lab tests can also play a role in some cases. A range of patient self-assessment scales have been developed, although there is no common understanding among pain specialists of where severe pain begins and ends.
The Visual Analogue Scale asks patients to rate the intensity of their pain on a scale ranging from 0mm to 100mm, where 100mm is ‘the maximum imaginable pain’ (which some experts explain as ‘burning alive’).
The 11-point Numeric Rating Scale is also based on equating pain to a number, whereas the Verbal Rating Scale requires patients to express their pain intensity in words (‘no pain’ versus ‘worst pain imaginable’). For younger patients, the Smiley Scale uses five faces with different expressions to indicate various intensities.
These tools have come under fire from some experts who believe they rely too heavily on subjective estimation of pain severity. Others say the link between subjective pain estimates and treatment goals should be defined.
An expert panel assembled as part of the Change Pain initiative has devised a new ten-point scale, which takes a more holistic approach, taking into account patients’ expectations on pain relief and quality of life improvement. Patients are asked to rate their current level of pain and to say what level would be tolerable.
Underlying mechanisms
When it comes to treating chronic pain, the three-step WHO pain ladder – which was originally developed for cancer pain – is often used in choosing treatment options. This system relies on pain intensity without taking account of the complexity of the underlying causes and pathways.
There is now a move in some quarters towards a mechanism-based approach, which would see treatment decisions based mainly on the underlying mechanism rather than severity alone.
This, according to Prof Morlion, requires a major educational effort to inform GPs and doctors-in-training of the recent shifts in thinking on pain management. The urgent need for educational outreach is illustrated by a European survey of 5,000 chronic pain sufferers, which found that only 2 per cent were being treated by a pain specialist. Pain is dealt with either by GPs or by patients using over-the-counter analgesics.
Genetic illnesses
“We need a mechanism-oriented way of thinking about pain. My worry is that teaching on pain management was only introduced in recent years. In my own case, I have to defend eight teaching hours a year against other specialists who want to teach about genetic illnesses GPs will rarely see,” said Prof Morlion.
Take lower back pain, for example. It frequently has both nociceptive and neuropathic causes, but this is often overlooked. Neuropathic pain is associated with higher pain intensity and longer duration of suffering and usually requires more than one medication to target the different underlying causes.
Different pain levels
Pharmacological treatment includes a wide range of analgesics for different pain levels: non-opioid analgesics, such as Non-Steroidal Anti-Inflammatory Drugs as (NSAIDs) or paracetamol for treating mild pain, and classical opioids, which are classified as weak and strong opioids. Weak opioids, like tramadol or codeine, are used in moderate pain conditions, while patients with severe pain are treated with strong classical opioids – typically morphine and oxycodone.
Opioids are commonly combined with non-opioid analgesics for the treatment of moderate to severe pain. In addition, adjuvant therapies that have primary indications other than for pain management but have analgesic properties in some pain conditions, especially those of neuropathic origin, may also be used. Examples of these medications include tricyclic antidepressants and anticonvulsants.
Other non-pharmacological options include psychotherapy, physiotherapy and cognitive-behavioural therapy (CBT).
However, treatment gaps remain and scientists have been closing in on new medicines designed to target pathways that amplify pain.
Any attempt to move pain management forward must capitalise on what researchers have learned about pain pathways, while remaining conscious of the need to minimise side effects.
The vicious circle that can arise when patients struggle to balance adequate pain relief with the ability to tolerate prescribed medicines too often leads them to discontinue treatment.
Around 30 per cent of patients stop their chronic pain treatments due to side effects, according to clinical studies. These often include gastrointestinal effects – particularly nausea, vomiting and constipation – as well as central nervous system disorders.
“In order to improve the pharmacological management of severe chronic pain, apart from correctly identifying the underlying pain mechanisms, it is crucial to have treatment options with good efficacy and a better tolerability profile available that can help overcome the current limitations,” concluded Prof Morlion.