Chronic pain

Chronic pain is defined as pain which persists despite adequate time for healing. There is no clear definition but it is often defined as pain that has been present for more than 12 weeks. Chronic pain tends to be very difficult to manage because of its complex natural history, mixed aetiology and poor response to therapy.

Chronic pain is not simply a physical problem. It is often associated with severe and extensive psychological, social and economic factors. Apart from poor general physical health and disability there may also be depression, unemployment, and family stress. Many of these factors interact, and the whole picture needs to be be considered when managing individual patients. The impact of chronic pain on patients' lives varies from minor restrictions to complete loss of independence.

Perception of pain is a complex process. Assessment and management can be a challenge. Intensity of pain does not always appear to fit in with the degree of perceived tissue injury, and is affected by a number of factors and mechanisms, and there may often be an overlap in the recognised categories of pain types. Moreover, National Institute for Health and Care Excellence (NICE) guidelines remind us that, whilst analgesics can be effective for pain relief, we must expect them to fail in the majority of patients.¹ The focus should be on improving quality of life, and non-pharmacological options as well as analgesia must be explored. Excessive prescribing of analgesics, particularly opioid analgesics, has the potential to do more harm than good.

Epidemiology

Prevalence figures vary depending on definition, but it is estimated that 13% of adults in the UK, and 20% in Europe, experience chronic pain. A UK-based systemic review and meta-analysis of population studies found that chronic pain affects between one third and one half of the population of the UK, and that between 10.4% and 14.3% of the population of the UK report moderately to severely disabling chronic pain.² The incidence increases with age, due to conditions such as osteoarthritis.

In the UK, it is estimated that 49% of those with chronic pain have depression.

Assessment³

Assessment should include a concise history, examination and bio-psychosocial assessment, identifying the type of pain (neuropathic/nociceptive/mixed), severity, functional impact and context.

Biomedical assessment

• Thorough pain history assessing each discrete pain (site, character, intensity, onset, precipitants, duration, intensity, exacerbating and relieving factors, night pain, perceived cause), systemic symptoms, past medical history.

• Physical examination (including behavioural response to examination).

• Previous investigations (and the patient's understanding).

• Previous and current treatment (including response, specialised treatments, side-effects, misconceptions, fixed beliefs, messages from other health professionals).

Psychological assessment

• Consider low mood, anxiety or depression.

• Psychiatric history, alcohol and illicit drug use, misuse, dependence or addiction, history of physical or sexual abuse.

• Identify yellow flags (see below), loss of confidence, poor motivation, reluctance to modify lifestyle, unrealistic expectations of self and others.

Social assessment

Ability to self-care, occupational performance, influence of family on pain behaviour, dissatisfaction at work, secondary gain (family overprotection, benefits, medico-legal compensation).

Yellow flags

Identify those at risk of a poor outcome. Yellow flags are indicators suggesting increased risk of progression to long-term distress, disability and pain (red flags are clinical indicators of possible serious underlying conditions).

Biomedical yellow flags: severe pain or increased disability at presentation, previous significant pain episodes, multiple site pain, non-organic signs, iatrogenic factors.

Psychological yellow flags: belief that pain indicates harm, an expectation that passive rather than active treatments are most helpful, fear avoidance behaviour, catastrophic thinking, poor problem-solving ability, passive coping strategies, atypical health beliefs, psychosomatic perceptions, high levels of distress.

Social yellow flags: low expectation of return to work, lack of confidence in performing work activities, heavier work, low levels of control over rate of work, poor work relationships, social dysfunction, medico-legal issues.

Associated diseases

• Major depression

• Somatic symptom disorder

Differential diagnosis

There are numerous causes of chronic pain. Some cases of chronic pain are due to identifiable and specific condtions - for example, osteoarthritis, low back pain, postherpetic neuralgia, cancer, irritable bowel syndrome, nerve root entrapment pains, such as sciatica and persisting pain following an acute injury including complex regional pain syndrome. In other cases, no specific condition or cause can be found.

Some of the causes of diffuse musculoskeletal pain (some of which will be treatable) to consider include:

• Rheumatoid arthritis.

• Spondyloarthropathy - eg, ankylosing spondylitis, reactive arthritis

• Vasculitis.

• Polymyositis, dermatomyositis.

• Polymyalgia rheumatica.

• Toxin-related - eg, eosinophilia-myalgia syndrome, silicone implants.

• Osteomalacia.

• Chronic fatigue syndrome.

• Fibromyalgia.

• Hyperthyroidism.

• Hypothyroidism.

• Multiple sclerosis.

Investigations

Although it is essential to make an accurate diagnosis regarding any underlying aetiology for the pain, a great deal of care and skill is often required to avoid unnecessary and inappropriate investigations and referrals, which only serve to increase the underlying anxiety of the patient and their family. A balance must be struck between ensuring that important and/or treatable conditions are excluded whilst in some cases avoiding an endless quest for a physical diagnosis.

Management

See also the separate Pain and Pain Relief and Neuropathic Pain and its Management articles. Articles on individual specific individual pain syndromes - such as Fibromyalgia, Low Back Pain and Sciatica, etc - may be helpful.

The optimum approach is likely to involve other members of the multidisciplinary team, including nurses, pharmacists, physiotherapists, psychological therapists, counsellors and occupational therapists. It may also include liaison with social services, employers and benefits agencies.

Encouraging the patient to have an attitude of positive coping is beneficial. A compassionate, patient-centred approach to assessment and management of chronic pain is likely to improve the chances of successful outcome.

Self-management should be encouraged from an early stage of a pain condition and as part of a long-term management strategy. There are no proven, comprehensive treatments in primary care for patients with medically unexplained symptoms.⁴ Management must be tailored for each individual patient.

The treatment should not just be aimed at pain relief but also at changing pain behaviour and improving function. The goals of treatment must be realistic and should be focused on restoration of normal function (minimal disability), better quality of life, reduction of use of medication and prevention of relapse of chronic symptoms.⁵

Referral to a specialist pain management service should be considered when non-specialist management is failing, chronic pain is poorly controlled, there is significant distress, and/or where specific specialised intervention or assessment is considered.

Pharmacological management

An increasing awareness of rising rates of opioid prescriptions and costs and, in some cases, related deaths has prompted guidelines on the judicious use of pharmacological agents in chronic pain from a number of organisations including NICE and the BMA in the UK, as well as others worldwide. Ensure that patients are made aware of the risks of pharmacological treatments, and of the non-pharmacological alternatives available.

Non-opioid analgesics

• Non-steroidal anti-inflammatory drugs (NSAIDs) should be considered in the treatment of patients with chronic nonspecific low back pain. When prescribing NSAIDs, consider potential gastroenterological and cardiological adverse effects and assess the individual's risk.

• Paracetamol should be considered alone or in combination with NSAIDs in the management of pain in patients with hip or knee osteoarthritis in addition to non-pharmacological treatments.

• Topical NSAIDs should be considered in the treatment of patients with chronic pain from musculoskeletal conditions, particularly for patients who cannot tolerate oral NSAIDs.

• Topical capsaicin patches should be considered in the treatment of patients with peripheral neuropathic pain when first-line pharmacological therapies have been ineffective or not tolerated. (This is from SIGN guidance for chronic pain - NICE guideline on neuropathic pain advises this is only used under specialist advice, although it gives capsaicin cream as an option.)⁶

• Topical lidocaine should be considered for the treatment of patients with postherpetic neuralgia if first-line pharmacological therapies have been ineffective.

• Topical rubefacients should be considered for the treatment of pain in patients with musculoskeletal conditions if other pharmacological therapies have been ineffective.

Opioids

• Over recent years there has been a significant increase in prescribing of opioids in the UK for chronic, non-cancer pain. There is no good-quality evidence to support the use of opioids in this situation.⁷

• Strong opioids should not be offered to treat chronic low back pain.⁸

• Strong opioids may be considered as an option for pain relief for patients with osteoarthritis if alternative analgesia has not been tolerated or effective, but only continued if there is ongoing pain relief.

• Tramadol, oxycodone and morphine are not recommended for chronic neuropathic pain unless under advice from a specialist.^{6 9}

• The minimal effective dose should be used. All patients on strong opioids should be assessed regularly for changes in pain relief, side-effects and quality of life, with consideration given to a gradual reduction to the lowest effective dose.

• It may be necessary to trial more than one opioid sequentially, as both effectiveness and side-effects vary between opioids.

• Signs of abuse and addiction should be sought at re-assessment of patients using strong opioids.

• Specialised referral or advice should be considered if there are concerns about rapid-dose escalation with continued unacceptable pain relief, or if more than 180 mg/day morphine equivalent dose is required.

Anti-epilepsy drugs^{6 10}

• Pregabalin and gabapentin can lead to dependence and should be prescribed appropriately to reduce the risks of misuse or dependence.

• Gabapentin should be considered for the treatment of patients with neuropathic pain.

• Pregabalin is recommended for the treatment of patients with neuropathic pain if other first- and second-line pharmacological treatments have failed.

• Pregabalin is recommended for the treatment of patients with fibromyalgia.

• A 2017 Cochrane review concluded that high doses of gabapentin can give good levels of pain relief to some people with postherpetic neuralgia and peripheral diabetic neuropathy, but there is limited evidence of benefit for other conditions.¹¹ Over half will not have worthwhile pain relief and may have adverse effects. A Cochrane review of pregabalin had similar findings.¹²

• Failure to respond after an appropriate dose for a test period should result in stopping pregabalin or gabapentin and a trial of a different medication.

• SIGN recommends that carbamazepine should be considered for the treatment of patients with neuropathic pain. A Cochrane review assessed it as being probably effective in some, but further studies are needed as evidence is limited.¹³ NICE recommends carbamazepine as first-line treatment for trigeminal neuralgia.

Antidepressants

• Patients with chronic pain conditions who are using antidepressants should be reviewed regularly.

• Tricyclic antidepressants should not be used for the management of pain in patients with chronic low back pain, although they may be considered for sciatica.

• Amitriptyline (25-125 mg/day) should be considered for the treatment of patients with fibromyalgia and neuropathic pain (excluding HIV-related neuropathic pain), although a recent Cochrane review found little convincing evidence of its benefit for neuropathic pain.¹⁴

• Serotonin-noradrenaline reuptake inhibitors (SNRIs) may be superior in efficacy and with regard to adverse effects.

• Duloxetine should be considered for the treatment of patients with diabetic neuropathic pain if other first- or second-line pharmacological therapies have failed. Duloxetine should be considered for the treatment of patients with fibromyalgia or osteoarthritis.

• Fluoxetine should be considered for the treatment of patients with fibromyalgia.

• Depression is a common comorbidity with chronic pain. Patients should be monitored and treated for depression when necessary.

• Amitriptyline, citalopram, duloxetine, fluoxetine, paroxetine or sertraline, can be used for people aged 18 years and over to manage chronic primary pain, after a full discussion of the benefits and harms. In April 2021, this was an off-label use of these antidepressants.

Cannabis-related medicinal products

NICE¹⁶ does not recommend that cannabis-based medicinal products (nabilone, dronabinol, delta-9-tetrahydrocannabinol (THC), or combination cannabidiol (CBD) with THC) be used for managing chronic pain.

However, patients already taking this medication before the guidance was issued in 2019 should be allowed to continue treatment until it is considered appropriate to stop.

Non-pharmacological management

With ever-increasing recommendations against many analgesics along with little evidence of efficacy, alternative interventions become appealing. There is some evidence of value in some chronic pain situations, but they generally involve referral to a specialist team.

• Referral to a multidisciplinary pain management programme should be considered for patients with chronic pain.

• Options within these programmes include:

  • Patient education (examination, information, reassurance and advice to stay active) - this may help them continue to work.

  • Relaxation methods¹⁷ .

  • Psychotherapy: behavioural and cognitive psychotherapies.

  • Physiotherapy.

  • Occupational therapy.

• Perception of pain is linked to emotional, cognitive and social functioning, and pain often affects mental health, so it is important to consider psychological aspects.

• Health professionals should be aware of the possibility that their own behaviour, and the clinical environment, can impact on reinforcement of unhelpful responses.

NICE says consider acceptance and commitment therapy (ACT) or cognitive behavioural therapy (CBT) for pain for people aged 16 years and over with chronic primary pain. There was not enough evidence to support a preference for ACT over CBT or CBT over ACT.

Cognitive behavioural therapy
Evidence shows that CBT for pain improves quality of life for people with chronic primary pain. A consistent benefit was not demonstrated in other outcomes but there was no strong evidence of harm. Economic evaluations show CBT to be cost effective.

Acceptance and commitment therapy
Evidence shows that ACT improves quality of life and sleep, and reduces pain and psychological distress. Although clinical evidence was from a fairly small number of studies, NICE agreed that ACT was likely to offer a good balance of benefits and costs and so recommended that it should be considered as a psychological therapy for chronic primary pain.

Exercise and physical therapy
Evidence (in 23 studies) showed that exercise reduced pain and improved quality of life (in 22 studies) compared with usual care in people with chronic primary pain. Benefit was seen for both short‑ and long‑term follow-up and was consistent across different types of exercise.

Most of the evidence was for professionally led supervised group exercise and for women with fibromyalgia or people with chronic neck pain. There is limited evidence comparing different types of exercise with each other.

Manual therapy

• Manual therapy (including manipulation and mobilisation) should be considered for short-term relief of pain for patients with chronic low back pain. NICE guidance on back pain advises this only be used as part of a treatment package which includes exercise and possibly also psychological therapy⁸ .

• Manual therapy, in combination with exercise, should be considered for the treatment of patients with chronic neck pain.

Exercise

• Exercise and exercise therapies are recommended in the management of patients with chronic pain.

• Advice to stay active should be given in addition to exercise therapy for patients with chronic low back pain, to improve disability in the long term. Advice alone is insufficient.

• Group exercise programmes are recommended for chronic low back pain⁸ .

• The following approaches should be used to improve adherence to exercise:
  

  • Supervised exercise sessions.

  • Individualised exercises in group settings.

  • Addition of supplementary material.

  • Provision of a combined group and home exercise programme.

Electrical therapies for chronic pain

NICE advises not to offer transcutaneous electrical nerve stimulation (TENS), ultrasound or interferential therapy to people aged 16 years and over to manage chronic primary pain because there is no evidence of benefit.

Complementary therapies

Acupuncture or dry needling should be considered for patients with chronic low back pain, osteoarthritis and chronic primary pain. A single course within a traditional Chinese or Western acupuncture system, for people aged 16 years and over, can be considered if the course:

• Is delivered in the community.
  

• Is delivered by a healthcare professional with appropriate training.

• Is made up of no more than five hours of healthcare professional time.

Other interventions

Nerve blocks and surgical spinal interventions may be helpful in some circumstances.

Complications

Chronic pain has a detrimental effect on physical health, daily activity, psychological health, employment and economic well-being. It can result in:

• Prolonged physical suffering.

• Depression.

• Adults and adolescents who suffer from chronic pain being at increased risk of suicidal thoughts and attempted suicide¹⁸ .

• Sleep disturbance.

• Marital or family problems.

• Negative effects on work, and loss of employment¹⁹ .

• Disability.

• Adverse medical reactions from long-term therapy, including side-effects, interactions, dependence and misuse. Adolescents with chronic pain are at increased risk of misusing opiates in adulthood²⁰ .

Prognosis

• The prognosis is variable but often poor.

• However, considerable improvement is possible with suitable support and management.

• The BMA points out that sufficient investment and resources for primary care, including longer consultation times, are required to support improvements in analgesic prescribing for patients with chronic pain .