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neuropathic pain

neuropathic pain modulators

types of neuropathic pain include:

  • diabetic neuropathy - pain in feet/ankles in up to 15% of diabetics
  • post-herpetic neuralgia - 7-27% with past herpes zoster & incidence increases with age
  • uncommonly referred neuropathic leg pains may occur in patients with genital Herpes simplex virus (HSV)
  • trigeminal neuralgia - sudden, brief, very severe paroxysms of pain - 5-8 per 100,000 people per year, females 2x males.

general principles of Mx

  • managing neuropathic pain is challenging - only half of those treated gain partial pain relief
  • treat early to prevent transition to persistent pain
  • once established, it is difficult to treat particularly when neuronal damage is irreversible.
  • unless there is nociceptor stimulation, most neuropathic pain is refractory to simple analgesics although a short course can be tried and thus the role for opiates and opioids is limited.
  • non-drug strategies may be of benefit
  • there is limited evidence for the efficacy of these drugs hence no generally accepted step-wise approach.
  • start with one drug at a time & allow a trial period to assess response
    • for diabetic or zoster pain, usually start with an antidepressant or an anticonvulsant such as gabapentin.
      • tricyclic antidepressants appear to relieve pain independent of their antidepressant action, and at smaller doses:
        • amitryptiline (Endep)or nortryptiline:
          • start at 10mg at night and increase by 10mg every 7 nights to a maximum dose of 150mg nocte.
        • start with 100mg tds, increase to 300mg tds over 7 days, increase by 100-300mg every 5 days to max. 3600mg daily.
      • other options for diabetic neuropathy pain:
        • topical capsaicin 0.075%
        • carbamazepine 200mg bd to qid
        • opiates and opioids eg. oxycodone 10-100mg daily, tramadol 100-400mg daily
        • pregabalin 150-600mg daily
        • serotonin-NA reuptake inhibitors:
          • venlafaxine 150-225mg daily
          • duloxetine 60-120mg daily
      • other options for herpetic pain:
        • pregabalin 75mg bd, if needed, increase to 150mg bd after 7 days then to maximum dose of 300mg bd after further 7 days.
        • topical capsaicin 0.075%
        • topical lignocaine
        • limited evidence for opiates and opioids:
          • tramadol 50mg daily increase by 50mg evry 3-4 days to to 100mg qid
    • trigeminal neuralgia
        • 50-100mg once or twice daily, gradually increase up to 400-800mg in 2-4 divided doses (max. 1600mg per day)
        • after 1 month pain free, gradually taper then stop
        • if not tolerated, or ineffective, consider:
          • oxcarbazepine (an analogue of carbamazepine)
            • seems to be effective for up to 3-4 years in up to two thirds of those who cannot tolerate carbamazepine or its efficacy has declined.
            • 150mg bd, increase to 300mg evry 3 days if needed to usual dose 300-600mg bd (max. dose 900mg bd)
            • no PBS approval other than for Rx epilepsy!
            • gabapentin
            • lamotrigine
            • phenytoin
          • referral to neurosurgery
neuropathic_pain.txt · Last modified: 2013/04/07 10:56 (external edit)