Red flags
- New back pain + neurological signs (weakness, sensory level, sphincter disturbance) -> spinal cord compression - emergency, MRI within 24h
- Sudden severe headache or new focal neurology -> cerebral metastasis with bleed/raised ICP
- Bone pain + hypercalcaemia symptoms (confusion, constipation, polyuria) -> malignant hypercalcaemia
- Pain with fever in a neutropenic patient -> neutropenic sepsis pathway takes priority
- Sudden severe pain at a known bone metastasis site -> pathological fracture
Differential by mechanism
By pain mechanism - determines analgesic choice
- Nociceptive somatic - bone metastases, soft tissue infiltration - well-localised, aching/throbbing
- Nociceptive visceral - hepatic capsule stretch, bowel obstruction - poorly localised, cramping/deep
- Neuropathic - nerve/plexus infiltration or compression, chemotherapy-induced peripheral neuropathy - burning, shooting, allodynia
- Breakthrough pain - transient exacerbation on a background of otherwise controlled pain, +/- predictable triggers (incident pain e.g. movement, weight-bearing)
Non-mechanical contributors
- Total pain concept - psychological distress, spiritual/existential distress, social factors all amplify perceived pain and must be addressed alongside pharmacology
- Treatment-related pain - mucositis, post-surgical, radiation-induced
Focused history
- Site, character, radiation, temporal pattern (constant vs breakthrough), severity (validated scale)
- Aggravating/relieving factors - movement (bone), eating (visceral), position
- Current analgesic regimen, response, side effects, adherence
- Impact on function, sleep, mood
- Screen for red flag features (above) at every assessment, not just at first presentation
- Psychosocial and spiritual distress - part of comprehensive assessment, not an afterthought
Focused examination
- Localise the pain generator - palpate for tenderness, examine the relevant dermatome/myotome if neuropathic pain suspected
- Full neurological exam if any suggestion of cord/nerve root compression - do not skip this in back pain
- Abdominal exam if visceral pain suspected (hepatomegaly, obstruction signs)
- Signs of opioid toxicity (sedation, myoclonus, pinpoint pupils, reduced respiratory rate) at every review
Investigation strategy
- Directed by the suspected pain generator and red flags, not routine imaging for all pain
- Urgent MRI spine for any suspected cord compression
- Bone scan/CT/MRI for suspected new bony metastasis causing localised pain
- Bloods - calcium (hypercalcaemia as a pain amplifier and red flag), renal function (guides opioid choice/dose adjustment)
Management
A. WHO analgesic ladder - still the organising framework, now used more flexibly
- Mild pain: non-opioid (paracetamol, NSAID if not contraindicated)
- Moderate pain: weak opioid (or low-dose strong opioid, increasingly preferred over historical step 2 agents) +/- non-opioid/adjuvant
- Severe pain: strong opioid (morphine, oxycodone, hydromorphone) titrated to effect - no ceiling dose, titrate against analgesia vs side effects
- Modern practice often moves directly to low-dose strong opioids for moderate-severe pain rather than strictly stepping through weak opioids
B. Opioid principles
- Immediate-release for titration and breakthrough dosing; convert to modified-release once stable dose established
- Breakthrough dose = ~1/6 to 1/10 of total daily opioid dose, available PRN
- Anticipate and manage side effects proactively - prescribe a laxative with every opioid (constipation near-universal, does not tolerate), antiemetic for initial nausea, monitor sedation
- Renal impairment - avoid morphine accumulation (active metabolites); fentanyl or buprenorphine preferred
C. Adjuvant analgesics by mechanism
- Bone pain: NSAIDs, bisphosphonates or denosumab (also reduce skeletal-related events), radiotherapy for localised refractory bone pain, corticosteroids
- Neuropathic pain: gabapentinoids (gabapentin, pregabalin), or tricyclic antidepressants (amitriptyline), or duloxetine
- Raised ICP/nerve compression oedema: dexamethasone
- Visceral/obstruction-related: antispasmodics, corticosteroids, octreotide for bowel obstruction symptoms
D. Interventional and non-pharmacological options for refractory pain
- Nerve blocks (e.g. coeliac plexus block for pancreatic cancer pain), vertebroplasty for painful vertebral collapse, palliative radiotherapy for localised bone pain
- Psychological support, physiotherapy, integrative approaches alongside pharmacology
E. Total pain approach
- Address psychological, social, spiritual distress concurrently - palliative care team involvement early for complex or refractory pain, not only at end of life
Traps
- Missing spinal cord compression because back pain was attributed to "known bone metastases" without a neurological exam
- Under-dosing opioids from fear of dependence/respiratory depression in a patient with genuine severe cancer pain - tolerance and titration make this manageable
- Forgetting to co-prescribe a laxative with an opioid
- Treating all pain as nociceptive and missing a neuropathic component that needs an adjuvant, not just more opioid
- Not involving palliative care early because pain is seen as a purely pharmacological problem
Talk track
Classify pain by mechanism first (somatic, visceral, neuropathic, breakthrough) - it determines which drug class helps. Titrate opioids without a ceiling against analgesia vs side effects, always with a laxative co-prescribed, and add mechanism-matched adjuvants (bisphosphonates/radiotherapy for bone, gabapentinoids for neuropathic, dexamethasone for compression-related oedema). Screen for red flags (especially cord compression) at every pain assessment, and address the psychological and social dimensions of total pain alongside the pharmacology.
8 of 8 sections written · drafted 2026-09-13