Key Facts

Pain is one of the most common reasons for seeking medical attention. Effective pain management requires assessment of pain type (nociceptive, neuropathic, mixed), severity, and underlying cause. The goal is to improve function and quality of life, not just reduce pain scores.

Epidemiology

• Chronic pain affects ~28% of UK adults (~28 million people)
• ~7.8 million people in UK live with chronic pain that is moderate to severely disabling
• Opioid prescribing in UK has increased significantly — ~5.6 million opioid prescriptions/quarter

Pain Classification

• Nociceptive: tissue damage — somatic (musculoskeletal, well-localised) or visceral (poorly localised, referred)
• Neuropathic: nerve damage — burning, shooting, tingling, allodynia; requires specific treatment
• Nociplastic: altered nociception without tissue/nerve damage — fibromyalgia, chronic widespread pain
• Mixed: combination — common in cancer pain, post-surgical pain

Pathophysiology

• Nociceptive: tissue damage → inflammatory mediators (prostaglandins, bradykinin) → nociceptor activation → ascending pathways → pain perception
• Neuropathic: nerve injury → ectopic discharges, central sensitisation, wind-up phenomenon → spontaneous/amplified pain
• Central sensitisation: repeated nociceptive input → dorsal horn hyperexcitability → amplified pain response
• Descending modulation: serotonin, noradrenaline pathways from brainstem → modulate pain transmission — target for amitriptyline, duloxetine

Pain Assessment

• Location, character, severity (numerical rating scale 0–10), timing, aggravating/relieving factors
• Neuropathic features: burning, shooting, tingling, electric-shock, allodynia (pain from non-painful stimulus), hyperalgesia
• Functional impact: sleep, mood, activity, work
• DN4 questionnaire or LANSS score: screening tools for neuropathic pain

Red Flags (Acute Pain)

• Cauda equina syndrome: saddle anaesthesia, urinary retention, bilateral leg weakness
• Acute abdominal pain with haemodynamic instability → surgical emergency
• Chest pain → exclude MI, PE, aortic dissection
• Sudden severe headache → exclude SAH

Red Flags (Chronic Pain)

• Escalating opioid doses without benefit
• Signs of opioid misuse/dependence
• New neurological deficit
• Unexplained weight loss with pain → malignancy

Clinical Assessment

• Pain history and examination: essential first step
• Pain scales: NRS (0–10), VAS, Brief Pain Inventory
• Neuropathic screening: DN4, LANSS
• Functional assessment: impact on daily activities, sleep, mood

Investigations (Guided by Cause)

• Bloods: FBC, CRP, ESR (inflammation/infection), bone profile (myeloma)
• Imaging: X-ray, MRI (spinal cord/nerve compression, bone disease)
• Nerve conduction studies: if neuropathy suspected
• Drug monitoring: opioid levels not routine; assess compliance, abuse (urine drug screen)

Special Tests

• Psychological assessment: PHQ-9, GAD-7 — chronic pain frequently coexists with depression and anxiety
• QST (quantitative sensory testing): specialist — assesses somatosensory function

WHO Analgesic Ladder

Step 1: Non-Opioid

• Paracetamol 1 g QDS (max 4 g/day; reduce in liver disease or low weight)
• ± NSAID (ibuprofen 400 mg TDS, naproxen 500 mg BD) with PPI cover

Step 2: Weak Opioid

• Codeine 30–60 mg QDS (max 240 mg/day) + paracetamol
• Or tramadol 50–100 mg QDS (caution: serotonin syndrome, seizures)
• Always prescribe laxative (senna or docusate) and antiemetic (cyclizine, ondansetron PRN)

Step 3: Strong Opioid

• Morphine: immediate-release 5–10 mg 4-hourly (opioid-naïve) → convert to modified-release once stable
• Breakthrough dose: 1/6 of total daily morphine dose
• Alternatives: oxycodone, fentanyl patches (stable pain), buprenorphine
• See dedicated Opioid Prescribing topic

Neuropathic Pain (NICE CG173)

• First-line: amitriptyline 10 mg ON → titrate to 75 mg; OR gabapentin 300 mg OD → 600 mg TDS; OR pregabalin 75 mg BD → 300 mg BD; OR duloxetine 30–60 mg OD
• Second-line: switch to different first-line agent or combine
• Topical: capsaicin 0.075% QDS (localised) or lidocaine 5% plaster
• Specialist: tramadol (short-term only), ketamine infusion, spinal cord stimulation

Non-Pharmacological

• Exercise and physiotherapy: most effective non-drug intervention for chronic pain
• Psychological therapy: CBT, acceptance and commitment therapy (ACT)
• TENS: transcutaneous electrical nerve stimulation
• Pain management programmes: multidisciplinary — recommended by NICE for chronic primary pain

Referral Criteria

• Pain clinic: chronic pain not controlled by primary care management
• Palliative care: cancer pain, end-of-life symptom management
• Neurosurgery: spinal cord compression, nerve root compression
• Psychology: chronic pain with significant psychological comorbidity

• Acute pain: usually resolves with appropriate treatment of underlying cause
• Chronic pain: complex, multifactorial — rarely 'cured'; aim for functional improvement
• Opioids for chronic non-cancer pain: limited long-term benefit; significant risks (dependence, tolerance, hyperalgesia)
• Neuropathic pain: often partially responsive; may require combination therapy
• Multidisciplinary approach (pain management programme): best evidence for chronic pain outcomes

WHO Analgesic Ladder Summary

Neuropathic Pain First-Line Options (NICE CG173)