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In nature, pain is supposed to be a response to a noxious stimulus to
teach us to not do whatever we did that caused the pain in the first
place.
Pain is sensed by small fibers in the peripheral nervous system. They
relay the information to the spinal cord and then to the brain. Most
pain
medications that we think of - tylenol, aspirin, ibuprofen, codeine,
morphine, and other narcotics, are tested in models of pain that do
not involve
damage to the peripheral nervous system itself. Common pain models include
skin trauma, orthopedic surgery, child birth, and kidney stones.
When neurologists think of neuropathic pain, we are refering to pain
being caused by the peripheral nerve fibers themselves. Descriptions
of
neuropathic pain by patients typically include words such as burning,
shooting, stabbing, or electric like and not aching or crushing. The
distribution
of pain will be along the course of a particular peripheral nerve or
a group of nerves of similar length. For neuropathic pain, non-narcotic
pain
relievers are generally not helpful. Narcotic pain relievers typically
have initial success but typically patients have to keep increasing
the
dose. I am not aware of any narcotic medications being approved for neuropathic
pain by the FDA. Neurologist have learned that other types of medications
- such as tricyclic antidepressants, serotonin and norepinephrine reuptake
inhibitor (SSNRIs) and
some
anti-epileptic
drugs (AEDs)
are
very
useful in this type of pain. Topical anesthetics can also be useful.
The approach to a patient with neuropathic
pain when seen by a neurologist will be very different when seen by physicians
who consider themselves pain specialists.
The following are the medications currently FDA approved for neuropathic
pain and their indications. Gabapentin or Neurontin is FDA approved for
post-herpetic neuralgia. Duloxetine or Cymbalta is FDA approved for painful
diabetic peripheral neuropathiy. Carbamezepine or
Tegretol
or
Carbatrol
is FDA approved for facial pain. Pregabalin or Lyrica is FDA approved
for post-herpetic neuralgia and painful diabetic peripheral neuropathy.
Lidoderm - a topical anesthetic - is FDA approved for post-herpetic neuralgia.
It is common for physicians to use all of these medications for any pain
that
sounds
neuropathic.
We
typically
choose
the first medication
to
try based upon side effect profile and cost since it is not clear which
medication is more effective for most patients. Other commonly used medications
include Amitriptyline and other anticonvulsants such as keppra, trileptal,
and zonegran.
Some of the most frequent causes of neuropathic pain are reviewed in
separate articles but any shooting, stabbing, or burning type pain in
the distribution of a particular nerve can benefit from this approach.
It is important to try to identify the cause of the nerve injury and
fix
it where possible. Unfortunately, this is not usually possible.
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