Neuropathic pain

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Neuropathic pain

• Amy P. Abernethy, MD
• Duke Cancer Care Research Program
• June 6, 2008

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Nocioceptive
Neuropathic
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Diagnosis

• Descriptors
• Tingling, burning, stabbing, electrical,
  radiating, shooting, lancinating, shock-like,
  stinging
• Central pain
• Stocking glove
• Abnormal sensations
• Dysethesias spontaneous abnormal sensations
• Hyeralgesia - increased perception
• Hypethesia numbness or decreased feeling
  increased pain threshold
• Allodynia pain due to non-painful stimuli
• Numbness
• Prolonged after sensations

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Map to the Syndrome if Possible

• Radiculopathy / cauda equina
• Plexopathy
• Radiation-induced
• Peripheral neuropathy
• Disease related
• Chemotherapy induced
• Phantom pain
• Post-herpetic pain

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Treatment Approach
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Methadone conversion
Daily chronic oral morphine equivalent Morphine to methadone ratio
lt100 mg 31
100-300mg 51
300-600mg 101
600-800mg 121
800-1100mg 151
gt1100mg 201
USE WITH CAUTION These ratios are different
within individuals
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Drugs

• Tricyclic antidepressants
• Lidocaine patch
• 5, on/off
• Capsaicin
• 0.025 4 times daily
• Anti-convulsants

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Drugs

• Gabapentin
• start low, 100mg qd-tid and titrate up
• Duloxetine
• 60mg bid
• Pregabalin
• Gabapentin failure
• Start low and titrate, 50-150mg bid
• Ketamine
• How do I prescribe ketamine at Duke?

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More help

• Newer drugs (e.g. ziconatide, cannabinoids)
• Anesthesia pain service (acute chronic)
• Acupuncture
• Outpatient consult
• Clinical trials
• Induction pain management
• The future
• new drugs, receptor polymorphisms, better
  diagnostics, better interventions

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Neuropathic bone pain?

• Mantyh cancer bone pain model, Exp Neuro 2005

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