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Introduction

Chronic pain has an unclear definition but some examples include:

  • Pain that persists despite adequate time for healing
  • Pain for >12 weeks

It is a common presentation to general practice. Chronic pain exists in 12-20% of the population. It is estimated that 50% of those with chronic pain also have depression.

Chronic pain is often associated with significant disability, important psychological features (e.g. depression and anxiety) and socioeconomic factors, such as unemployment and family stress. It is often very difficult to treat.

Traditional analgesics are much more effective in acute pain as opposed to chronic pain, and in the majority of patients will not make a significant impact on their pain. Already comp[lex cases can be further complicated with medication addiction (particularly in regard to opiates).

Management should focus on all the factors involved, and aim for an improvement in quality of life, rather than the eradication of pain. Managing patient expectations around this can also be challenging.

In some cases, there is an obvious underlying medical cause, such as osteoarthritis, neuropathic pain (various causes), or an complication of an acute injury. However, in many cases, no specific underlying cause can be identified.

The assessment and management of pain can typically be divided into three areas:

  • Biomedical factors
  • Psychological factors
  • Social factors

Assessment and investigation

It is important to strike the right balance between thoroughly discerning a possibly treatable underlying cause, and over-investigating. In the acute and early stages, prudent history, examination and targeted investigation maybe warranted. However, in the chronic stable patient, it is important to properly assess the benefits of any further investigation. Frequently, investigation does not point to a specific diagnosis, and any minor abnormalities noted on scans can lead to further anxiety for patients, or in some cases, catasrophising, and over-focus of the patient on the often non-specific abnormalities of uncertain significance. (See “Yellow flags” below).

“Yellow flags”

Yellow flags are features that are associated with a poor out once in chronic pain. They can be divided into the three categories:

  • Biomedical factors
    • Multiple sites of pain
    • Non-organic signs
    • Severe pain on presentation
    • Severe disability at presentation
  • Psychological factors
    • Belief that pain indicates harm or ‘damage’ or some other significant pathological disturbance
    • Lack of motivation
    • Belief that passive treatment (i.e. medication) is more effective than active treatment (e.g. CBT, physiotherapy)
    • Avoidance of activities or behaviours due to belief that they will cause pain
    • Catastrophising
    • Belief in alternative therapies
  • Social factors
    • Expectation of not returning to work
    • Manual worker
    • Poor relationships with work colleagues
    • Lack of control of working conditions / work hours
    • Medico-legal issues

Differentials

Chronic pain is often considered a diagnosis in its own right, with or without an obvious underlying cause. Wherever possible an underlying cause should be treated. Some possible differentials include:

Investigation

  • Avoid over-investigation, which often increases anxiety
  • Can be difficult to find the right balance between appropriate and over-investigation
  • Attempt to rule out any treatable causes
  • Take time to explain investigation reasoning to patients

Management

Basic principles

  • Treat nay underlying cause
  • Involve a multidisciplinary team, typically include a GP, physiotherapist, practice nurses, pharmacists and possibly psychologist and pain specialist
    • Your plan may also involve addressing some of the social aspects associated with chronic pain – such as liaising with social services, employers and benefit agencies
  • Consider neuropathic pain treatment options
  • Encourage the patient to take charge of their symptoms and self-directed coping strategies
  • Treatment is not aimed at pain relief, but at improving (or maintaining) function and empowering patients
  • Minimise the use of medication and maximise function and quality of life

Pharmacological management

Non-opioid analgesia

  • Should be the mainstay of pharmacological treatment
  • Typically NSAIDs are used, but are of variable efficacy, and adverse effects, such as GORD or renal impairment are not insignificant
    • Most useful for lower back pain, but often used in other chronic pain disorders
    • Topical NSAIDs may be appropriate in some musculoskeletal disorders and / or where oral agents can’t be tolerated
  • Paracetamol also often used alone or inconjucntion with NSAIDs
    • Fewer adverse effects, but also tends to be less effective
  • Other novel agents may be recommended in some circumstances
    • Capsaicin cream or patches – may be useful in peripheral neuropathy
    • Topical lignocaine – may be useful in post-herpetic neuralgia

Opioid analgesia

In recent years there has been a large increase in the prescribing of opioids for chronic pain. There is NOT good evidence for the use of opiates in chronic pain, and they are easily abused.

In chronic pain, opiates:

  • Only provide meaningful pain relief in 30% of patients
  • In those 30% of patients, pain relief is typically rated by patients as being 30-50% effective, but 80% of patients report significant side effects
  • May be considered in certain circumstances as a “trial”

Examples include:

  • Codeine
  • Oxycodone (endone, oxycontin, Targin)
  • Morphine
  • Fentnayl
  • Buprenorphine
  • Tramadol
    • Tramadol is a special case. It is a synthetic drug with mu receptor (opioid) effects, as well as seretonergic effects
    • It should be used only with extreme caution with other serotonergic drugs such as SSRIs and TCAs due to the risk of serotonin syndrome.
    • It has a limited role in chronic pain for this reason – because these other drugs are also often used
    • It tends to have less sedative effects and fewer gastrointestinal effects than other opioids
    • Tapentadol is a similar synthetic drug, designed to have fewer adverse effects than tramadol

Despite this, opiates are still widely used for chronic pain. This probably occurs “accidentally” in many patients – where they are initially prescribed an opiates for acute pain – which then becomes chronic pain.

Circumstances where opiates analgesia should be considered in chronic pain would typically involve multiple of the following factors:

  • All other treatment options exhausted
  • Patient has already been involved with an MDT approach
  • Potential for abuse has been assessed
  • Advised of the expected outcomes – e.g. 30% of patient will expect a 30-50% reduction in pain

When prescribing opiates for chronic pain, some general advice includes:

  • Stay away from short acting opioids
  • Start with a low dose
  • Don’t start them at the same time as other pain medication
  • Try to stick to a single practitioner who is prescribing
  • Address constipation issues – typically involves prescribing laxatives with opioids
  • Avoid the co-prescription of benzodiazepines
  • Be open to trying different opioids if treatment with one is unsuccessful
  • Consider referral to a pain specialist in cases of rapidly escalating dose or a total daily dose of >180mg morphine equivalent

Tolerance and dependence can develop quickly and can be difficult to reverse.

Some common side effects of opioids include:

  • Constipation
  • Sedation
  • Sleep apnoea
  • Nausea and vomiting
  • Fluid retention
  • Gynaecomastia
  • Addiction (about 3-4% of patients – different to tolerance which a physiological response)
  • Hyperalgesia
    • Increased levels of pain and sensitivity to painful stimuli
    • In these circumstances increasing the opioids can increase the pain

Opiates use in chronic pain in cancer patient is considerate separately to the “non-malignant” pain which is discussed above.

Other pharmacological agents

Other agents are also often used in conjunction with the above measures. These tend to be of most use in patients with neuropathic pain – which will include a large portion of patients with chronic pain. These agents include:

  • Antidepressants – SSRIs, TCAs, SNRIs
  • Anti-epileptic drugs
  • For more information about these options – see the neuropathic pain article

Psychological interventions

Chronic pain typically co-exists with depression. Even when depression is not present, there is some evidence that psychological therapies can improve chronic pain.

  • The perception of pain is influence by social and psychological factors and thus learning to interpret these cues may help to reduce pain

Consider:

  • Referral to MDT
  • Referral to psychologist for Cognitive Behavioural Therapy
  • Relaxation therapies – e.g. mindfulness -w hick could be self-directed through free apps such as “smiling mind”
    • Some efficacy but probably less effective than CBT

Other interventions

  • Encourage regular exercise and to stay active – to minimise disability
  • Physiotherapy
  • Occupational therapy

Complications

  • Depression
  • Increased risk of suicidal ideation
  • Relationship problems
  • Sleep disturbance
  • Disability
  • More likely to be unemployed

References

  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy
  • Chronic pain - patient.info
  • Chronic Pain - eTG

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