Post on 17-Feb-2017
ALBERTO RIVERA SANCHEZ MD FAAPMR, ABPM, ABDA
PAIN MANAGEMENT SUB SPECIALIST
Managing Neuropathic Pain
Neuropathic pain Prevalence of 2-40% (Harden 2015)
3.75 million with chronic NP in the US (IASP 1997)
The most common studied NP syndromes are: DMPN PHN
Other causes:○ SCI○ Phantom Pain○ CRPS○ Post CVA○ Nerve Injury
Neuropathic pain 33% of pain patients seen in tertiary
facilities have anxiety disorders (Von Korff, et al 1996)
40-60% meet the criteria for depressive disorder (Banks, 1996)
FDA Approved Med’s for NP Carbamazepine Lidocaine patches Gabapentin Pregabalin (PHN, DMPN) Capsaicin Duloxetine (DMPN) Tapentadol ER (DMPN)
Off label Med’s for NP Anti-depressants Anti-epileptics Anti-arrythmic
Evidence for their safety and efficacy is lacking
Benbow 1999, Kost 1996, Karlsten 1997, Carter 1997
Central Sensitization Excitatory neurotransmitters (e.g. glutamate,
substance P, neurokinin A or CGRP) stimulate the dorsal horn neurons
Repeated pain stimuli activate the NMDA receptors (“wind-up”), which induce prolonged postsynaptic action potentials
Activation of the NMDA receptors raises intracellular Ca++
Expression of c-fos and c-jun genes leading to increased protein synthesis
Peripheral Sensitization
1° afferent nerve terminals (A-delta, C Fibers) hyperexcitability
Bradykinin, histamine, PG’s, cytokines, and substance P lower their action potential threshold
Mediators increase the gain of the inflammatory milieu
Spine 1997N. Harden 2015
Hyperalgesia Increased pain from a stimulus that
normally provokes pain (IASP 2012)
Treatment:Topical lidocaine 2.5% / prilocaine 2.5%Gabapentin (Pain 2002)
IV Lidocaine (Neurology 2000)
Capsaicin (Scholten 2015)
Allodynia Pain due to a stimulus that does not
normally provoke pain (IASP 2012) Treatment
Gabapentin (Eur Neurol 1998)
Pregabalin (J Pain 2008 )
Ketamine (Pain 1994)
IV Lidocaine (J Pain Symp Mgt 1999)
IV Morphine (Neurology 1991)Tramadol (Pain 1999)
Shooting pain Pain that seems to travel like lightning from
one place to another Treatment:
Amitriptyline (Neurology 1987)
Carbamazepine (Campbell et al. 1966)
Gabapentin (Eur Neurol 1998)
Imipramine (Neurology 2003)
Lamotrigine (Pain 1997)
IV Phenytoin (Anesth Analg 1999)
Venlafaxine (Neurology 2003)
TCA’s and Other Psych Med’s in NP
Help in NP due to Na+ channel blocking Risk of sedation and anticholinergic
effects
Capsaicin Selective stimulator of C-fibers Cause Substance P release Depletes Substance P Apply 3-4 times/day for 4-8 weeks Capsaicin 8% relief may last 12 weeks Start with tramadol or lidocaine cream
(Pain Ther 2014)
GABA, Pregabalin and NP
Pregabalin Side Effects
Infection peripheral edema, Fatigue constipation, weight gain blurred vision ataxia, dizziness headache diplopia
Drowsiness tremor visual field loss xerostomia accidental injury
Gabapentin and Opioids
Gabapentin Increases the concentration of GABA in
the Brain Modifies Ca2+ currents Excreted 95% unchanged in the urine Good for NP No direct anti-nociceptive effect
Gabapentin Side Effects
Sedation Fever Fatigue Ataxia Nystagmus Dizziness Drowsiness Weight gain due to increased apetite
Ketamine
Amantadine and Dextromethorphan are effective for DMPN (Pain 1998, Neurology 1997)
Herbal supplements Cannabis Plant Extract (AAPM&R 2015)
FMS NP RA Spasticity related pain
Side effects Dizziness Drowsiness Fatigue Legal issues
Herbal supplements Alpha Lipoic Acid 600mg daily L-carnitine 1000mg daily Vitamin B complex Vitamin D once a week CoQ10---FMS—150-300mg daily (PMR Journal 2015)
Non pharmacologic Tx PT OT Pain psychology Cognitive behavioral therapy Ergonomic evaluation Aqua therapy Work conditioning/hardening
Interventional Pain Management Spinal Cord Stimulators Intercostal nerve blocks Peripheral nerve blocks Caudal Epidural injections Sphenopalatine Ganglion Blocks Radiofrequency Neurotomy Stellate Ganglion Blocks
Conclusion The best management option is:
• Multimodal Therapy
Consider the patient’s comorbidities Listen to your patient complaints