Chronic pain: an overview for the generalist
- Concept
Chronic pain lasts more than three months; it changes the nervous system and daily life, so it is treated with several approaches, not pills alone.
What it is
Chronic pain is pain that persists or recurs for more than three months, beyond the usual time for tissue healing. It is common, a leading cause of disability, and often linked with poor sleep, low mood, anxiety and reduced work and social life. It is useful to sort it by mechanism. Nociceptive pain comes from ongoing tissue damage or inflammation, as in osteoarthritis. Neuropathic pain comes from a lesion or disease of the somatosensory nervous system, as in diabetic neuropathy, postherpetic neuralgia or nerve injury, and is described as burning, shooting or electric with numbness or allodynia. Nociplastic pain arises from altered pain processing without clear tissue or nerve damage, as in fibromyalgia. Many patients have mixed pain. Central sensitisation, in which spinal and brain pathways amplify signals, explains why pain can outlast its cause. The biopsychosocial model guides care: assess the pain, its impact on function, mood and sleep, beliefs and fears, and look for red flags of serious disease. Management combines education, graded physical activity, psychological therapies such as cognitive behavioural therapy, sleep care and medicines chosen by mechanism. Opioids have a limited role in chronic non-cancer pain because benefit is small and harms grow over time. Ketamine, an NMDA receptor antagonist, is used in specialist settings for some refractory pain. Persistent pain after surgery is a recognised form, and good acute pain control may reduce it.
Key points
- Red flags in back and other pain: weight loss, fever, history of cancer, night pain, new neurological deficit, bladder or bowel dysfunction.
- Measure function and goals (walking, work, sleep), not only a pain score.
- Depression, anxiety and catastrophising worsen pain and disability; treating them helps the pain.
- Exercise and staying active are effective in most chronic musculoskeletal pain.
- Persistent postsurgical pain is pain lasting beyond about three months after an operation, common after amputation, thoracotomy, breast and hernia surgery.
How it works
- Repeated pain input causes central sensitisation: spinal neurons fire more easily, partly through NMDA receptor activation.
- Descending inhibitory pathways that use serotonin and noradrenaline normally damp pain; antidepressants that raise these transmitters strengthen them.
- Gabapentinoids bind a subunit of voltage-gated calcium channels and reduce release of excitatory transmitters.
- Long-term opioid use can cause tolerance and opioid-induced hyperalgesia, so pain may worsen as the dose climbs.
Types of chronic pain
| Type | Mechanism | Examples | Drug classes often used |
|---|---|---|---|
| Nociceptive | Ongoing tissue damage or inflammation | Osteoarthritis, inflammatory arthritis | Paracetamol, NSAIDs, topical NSAIDs |
| Neuropathic | Lesion or disease of the somatosensory nerves | Diabetic neuropathy, postherpetic neuralgia, nerve injury | Tricyclics, SNRIs, gabapentinoids, topical lidocaine |
| Nociplastic | Altered pain processing without clear damage | Fibromyalgia, some chronic low back pain | Exercise and psychological therapy first; tricyclics or SNRIs |
In practice
- Agree realistic goals: less pain and better function, rarely a pain-free life.
- Choose drugs by mechanism and review benefit and harm at each visit; stop what does not help.
- Paracetamol and NSAIDs are for nociceptive pain; long-term NSAIDs carry gastrointestinal, renal and cardiovascular risks.
- If opioids are used, agree goals and a trial period, use the lowest effective amount, review often and taper when harms outweigh benefits.
- Refer to a pain service for complex, refractory or high-risk cases; options include interventional procedures and multidisciplinary programmes.
Next step
- Screen for red flags and investigate or refer urgently if present.
- Record pain, function, mood, sleep and goals, and agree a written plan with the patient.
- Start active treatment (education, physical activity, psychological support) alongside any medicine.
- Refer to a pain service or senior when pain is refractory, opioid use is escalating or there is suspected misuse.
- Follow up regularly to review benefit, side effects and whether each medicine should continue.
Test yourself
Think of the answer, then tap the question to see it.
How is chronic pain defined?
Pain that persists or recurs for more than three months, beyond the usual time for tissue healing.
What are the three mechanistic types of chronic pain?
Nociceptive (from tissue damage or inflammation), neuropathic (from a lesion or disease of the somatosensory nervous system) and nociplastic (altered pain processing).
Which drug classes are first-line for neuropathic pain?
Tricyclic antidepressants, SNRIs and gabapentinoids; topical lidocaine is useful for localised neuropathic pain.
Why is ketamine used in some refractory chronic pain?
It blocks NMDA receptors, which drive central sensitisation; it is used in specialist settings because of psychological, cardiovascular and urinary side effects.
Elsewhere in DurgiPedia
- Pain and temperature: pathways and modulation
- Pain assessment and pain scales
- Pain assessment scales: numeric, visual analogue, faces, behavioural (FLACC) and in dementia
- Non-drug pain relief: what nurses do
Connections
Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.
Sources: Chronic Pain (StatPearls (NCBI Bookshelf), 2025); Ketamine in Acute and Chronic Pain Management (StatPearls (NCBI Bookshelf), 2023).
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Representative model, for educational purposes only.