365.1 🎓 醫孞生版

365.1.0.1 📌 䞀頁重點

365.1.0.1.1 Pain Types

365.1.1 Nociceptive

  • Somatic: skin, muscle, bone, joint (well-localized, sharp, aching)
  • Visceral: organs (poorly localized, dull, referred)
  • Examples: post-op, fracture, MI

365.1.2 Neuropathic

  • Peripheral: diabetic neuropathy, postherpetic, CIPN, radiculopathy
  • Central: post-stroke, MS, spinal cord injury
  • Quality: burning, electric, lancinating, allodynia, hyperalgesia
  • Treatment: gabapentinoids, SNRIs, TCAs, topical

365.1.3 Nociplastic (Central Sensitization)

  • Altered nociception without clear tissue damage
  • Examples: fibromyalgia, IBS, TMD, chronic low back pain
  • Treatment: multimodal, less opioid-responsive

365.1.4 Mixed

  • Often combinations
365.1.4.0.1 Pain Assessment

365.1.5 Components

  • Location
  • Quality (sharp, dull, burning, electric, throbbing)
  • Severity (NRS 0-10, VAS, functional impact)
  • Timing (constant, intermittent, fluctuating)
  • Triggers/relievers
  • Associated symptoms
  • Impact on function, sleep, mood

365.1.6 Tools

  • Numeric Rating Scale (NRS)
  • Visual Analog Scale (VAS)
  • McGill Pain Questionnaire (qualitative)
  • Brief Pain Inventory (BPI)
  • DN4, painDETECT (neuropathic screening)
365.1.6.0.1 Treatment

365.1.7 WHO Analgesic Ladder

Step 1 (Mild, NRS 1-3): - Acetaminophen (1 g q6h max 4 g/d; hepatic caution) - NSAIDs (ibuprofen, naproxen, diclofenac, celecoxib, ketorolac) - GI, renal, cardiovascular risks - Adjuvants: caffeine, antispasmodics

Step 2 (Moderate, NRS 4-6): - Tramadol (weak Ό + SNRI; seizure risk) - Codeine (CYP2D6 variability) - Tapentadol (Ό + NRI) - Plus non-opioid

Step 3 (Severe, NRS 7-10): - Morphine (gold standard, PO, IV, SC; active metabolites — renal caution) - Oxycodone (PO, IR + ER) - Hydromorphone (more potent, less neurotoxic metabolites) - Fentanyl (transdermal patch, IV, intranasal) - Methadone (long T1/2, QT prolong, NMDA effect — useful for opioid-refractory neuropathic) - Plus non-opioid + adjuvant

365.1.8 Adjuvants (All Steps)

  • Antidepressants: TCAs (amitriptyline, nortriptyline), SNRIs (duloxetine, venlafaxine)
  • Anticonvulsants: gabapentin, pregabalin, carbamazepine (TN)
  • Topical: lidocaine 5% patch, capsaicin 8% patch
  • Corticosteroids: bone pain, neuropathic
  • Bisphosphonates: bone metastases
  • Cannabinoids: select cases
  • NMDA antagonists: ketamine

365.1.9 Adjuvant Therapies

  • Physical therapy
  • CBT, mindfulness
  • Acupuncture
  • TENS
  • Massage
365.1.9.0.1 Neuropathic Pain

365.1.10 Mechanisms

  • Ectopic firing
  • Ephaptic transmission
  • Central sensitization
  • Disinhibition
  • Glial activation

365.1.11 First-Line Drugs

  • Gabapentinoids (gabapentin 300-3600 mg/d, pregabalin 150-600 mg/d): dose-titrated
  • TCAs (amitriptyline 10-100 mg HS, nortriptyline): anticholinergic, sedation, CV
  • SNRIs (duloxetine 60-120 mg, venlafaxine 75-225 mg)

365.1.12 Second-Line

  • Topical lidocaine 5% patch (localized — PHN, focal)
  • Capsaicin 8% patch (PHN, HIV neuropathy)
  • Tramadol
  • Opioids (selected refractory cases)

365.1.13 Specific Conditions

Diabetic Peripheral Neuropathy: - Glycemic control - Pregabalin, duloxetine, gabapentin - Capsaicin patch

Postherpetic Neuralgia (PHN): - Gabapentin, pregabalin - TCA - Lidocaine 5% patch - Capsaicin 8% patch - Prevention: shingles vaccine (Shingrix), early antivirals

Trigeminal Neuralgia: - Carbamazepine first-line - Oxcarbazepine, lamotrigine, gabapentin - Microvascular decompression

Complex Regional Pain Syndrome (CRPS): - Type I (no nerve injury) + Type II (nerve injury) - Allodynia, autonomic, motor changes - Multimodal — physical therapy, anti-neuropathic agents, sympathetic blocks

365.1.13.0.1 Opioid Considerations

365.1.14 Equivalence Table (Oral Morphine Equivalents — MME/day)

Drug Conversion to MME
Morphine 1:1
Oxycodone 1.5:1
Hydromorphone 4:1
Fentanyl (TD ÎŒg/h) × 2.4
Methadone Variable (3-12:1 depending on dose)
Codeine 0.15:1
Tramadol 0.1:1

365.1.15 Side Effects

  • Constipation (predictable; prophylactic laxative)
  • Nausea (tolerance develops)
  • Sedation
  • Respiratory depression (high doses, combinations)
  • Pruritus
  • Endocrine (hypogonadism)
  • Hyperalgesia (paradoxical)
  • Dependence + tolerance + addiction

365.1.16 Opioid Use Disorder

  • Distinct from physical dependence
  • Risk factors: prior addiction, depression, young age, family history
  • Screening tools (ORT, SOAPP, COMM)
  • PDMP (prescription drug monitoring)
  • Naloxone for overdose
  • MAT (medication for addiction): buprenorphine, methadone, naltrexone

365.1.17 Tapering

  • Slow (10% per week typical)
  • Address withdrawal
  • Address underlying pain
  • Consider buprenorphine for chronic high-dose

365.1.17.1 🩺 床邊速查

  • Pain types: nociceptive (somatic, visceral) vs neuropathic vs nociplastic
  • WHO ladder: non-opioid → weak opioid → strong opioid; adjuvants throughout
  • Neuropathic first-line: gabapentinoids, TCAs, SNRIs
  • Trigeminal neuralgia: carbamazepine
  • PHN prevention: Shingrix vaccine
  • Opioids: minimize, prophylactic laxatives, taper slowly
  • MME: ≥ 50 MME/d high risk; ≥ 90 MME/d very high risk