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sanitation in Spain.
Postherpetic neuralgia (PHN) is a neuralgia caused by the varicella zoster virus.
Typically, the neuralgia is confined to a dermatomic area of the skin and follows an
outbreak of herpes
zoster (HZ, commonly known as shingles) in
that same dermatomic area. The neuralgia typically begins when the
HZ vesicles have crusted over and
begun to heal, but it can begin in the absence of HZ, in which case
zoster sine herpete is presumed (see Herpes zoster).
Treatment options for PHN include antidepressants, anticonvulsants (such
as gabapentin or pregabalin) and topical
agents such as lidocaine patches or capsaicin lotion. Opioid analgesics may also
be appropriate in many situations. There are some sporadically
successful experimental treatments, such as rhizotomy (severing or
damaging the affected nerve to relieve pain), and TENS (a type of electrical
Postherpetic neuralgia is thought to be nerve damage caused by
herpes zoster. The damage causes nerves in the affected dermatomic area of the skin to send
abnormal electrical signals to the brain. These signals may convey
excruciating pain, and may persist or recur for months or even
In the United States each year approximately 1,000,000
individuals develop herpes zoster. Of those individuals
approximately 20%, or 200,000 individuals, develop postherpetic
Less than 10 percent of people younger than 60 develop
postherpetic neuralgia after a bout of HZ, while about 40 percent
of people older than 60 do.
- Race: It may influence susceptibility to herpes zoster. African
Americans are one fourth as likely as Caucasians to develop this
- With resolution of the HZ eruption, pain that continues for 3
months or more is defined as PHN.
- Pain is variable from discomfort to very severe and may be
described as burning, stabbing, or gnawing.
- Area of previous HZ may show evidence of cutaneous scarring.
- Sensation may be altered over involved areas, in the form of
either hypersensitivity or decreased sensation.
- In rare cases, the patient might also experience muscle
weakness, tremor or paralysis — if the nerves involved also control
to seek medical advice
It is strongly recommended by professionals that patients see a
doctor at the first sign of shingles. Treating shingles early — within
three days of developing the rash — and aggressively with oral antiviral drugs may reduce the length and
severity of postherpetic neuralgia. In addition, amitriptyline may
reduce the risk of developing PHN.
If patients do develop postherpetic neuralgia, they are also
advised to see their doctor immediately. They may have to work with
their doctor and sometimes other specialists such as neurologists
to try a variety of treatments before they find something that
- No laboratory work is usually necessary.
- Results of cerebrospinal fluid (CSF)
evaluation are abnormal in 61%.
- Pleocytosis is
observed in 46%, elevated protein in 26%, and VZV DNA in 22%.
- These findings are not predictive of the PHN clinical
- Viral culture or immunofluorescence staining may be
used to differentiate herpes simplex from herpes zoster in cases
that are difficult to distinguish clinically.
- Antibodies to herpes zoster can be
measured. A 4-fold increase has been used to support the diagnosis
of subclinical herpes zoster (zoster sine herpete). However, a
rising titer secondary to viral exposure rather than reactivation
cannot be ruled out.
- Magnetic resonance imaging
(MRI) lesions attributable to HZ were seen in the brain stem and
cervical cord in 56% (9/16) of patients.
- At 3 months after onset of HZ, 56% (5/9) of patients with an
abnormal MRI had developed PHN.
- Of the 7 patients who had no HZ-related lesions on MRI, none
had residual pain.
Treatment for postherpetic neuralgia depends on the type and
characteristics of pain experienced by the patient. Pain control is
essential to quality patient care; it ensures patient comfort.
Possible options include:
agents, such as famciclovir, are given at the onset of
attacks of herepes zoster to shorten the clinical course and to
help prevent complications such postherpetic neuralgia. However
they have no role to play following the acute attack if
postherpetic neuralgia has become established.
- Locally applied topical
- Aspirin mixed into an appropriate solvent such as diethyl ether may
- Lidocaine skin
patches. These are small, bandage-like patches that contain the
topical, pain-relieving medication lidocaine. The patches,
available by prescription, must be applied directly to painful skin
to deliver relief for four to 12 hours. Patches containing
lidocaine can also be used on the face, taking care to avoid mucus
membranes e.g. eyes, nose and mouth.
- Systemically delivered
- Pain modification therapy
- Antidepressants. These drugs affect key
brain chemicals, including serotonin and norepinephrine, that play a role in both
depression and how your body interprets pain. Doctors typically
prescribe antidepressants for postherpetic neuralgia in smaller
doses than they do for depression. Low dosages of tricyclic antidepressants,
including amitriptyline, seem to work best for
deep, aching pain. They don't eliminate the pain, but they may make
it easier to tolerate. Other prescription antidepressants (e.g. venlafaxine, bupropion and selective serotonin
reuptake inhibitors) may be off-label used in postherpetic neuralgia
and generally prove less effective, although they may be better
tolerated than the tricyclics.
- Anticonvulsants. These agents are used
to manage severe muscle spasms and provide sedation in neuralgia.
They have central effects on pain modulation. Medications such as
Phenytek), used to treat seizures, also can lessen the pain
associated with postherpetic neuralgia. The medications stabilize
abnormal electrical activity in the nervous system caused by
injured nerves. Doctors often prescribe another anticonvulsant
called carbamazepine (Carbatrol, Tegretol) for
sharp, jabbing pain. Newer anticonvulsants, such as gabapentin
(Neurontin) and lamotrigine (Lamictal), are generally
tolerated better and can help control burning and pain.
- Corticosteroids are commonly prescribed
but a Cochrane Review found limited evidence and
- Anecdotal testimonies from patients have suggested that smoking
relieves the pain in much the same way as it relieves the pain of
In some cases, treatment of postherpetic neuralgia brings
complete pain relief. But most people still experience some pain,
and a few don't receive any relief. Although some people must live
with postherpetic neuralgia the rest of their lives, most people
can expect the condition to gradually disappear on its own within
High-Concentration Capsaicin Patch Granted Orphan Drug
Designation for PHN from:http://www.medscape.com/viewarticle/704117?sssdmh=dm1.489879&src=ddd
On June 9, 2009, The FDA approved orphan drug designation for a
high-concentration capsaicin dermal patch (Qutenza [formerly
NGX-4010], NeurogesX, Inc) for the treatment of pain associated
with postherpetic neuralgia (PHN). Relief of pain is possible up to
3 months with no to minimal side effects. Qutenza has been recently
approved by the FDA for general use in PHN. Distribution is planned
for the first half of 2010. See NeutrogesX for distribution
- The natural history of PHN involves slow resolution of the pain
- In those patients who develop PHN, most will respond to agents
such as the tricyclic antidepressants.
- A subgroup of patients may develop severe, long-lasting pain
that does not respond to medical therapy. Continued research for
new agents is necessary.
In 1995, the Food and
Drug Administration (FDA) approved the vaccine to prevent chickenpox. Its effect on
PHN is still unknown. The vaccine — made from a weakened form of
the varicella-zoster virus — may keep chickenpox from occurring in
nonimmune children and adults, or at least lessen the risk of the
chickenpox virus lying dormant in the body and reactivating later
as shingles. If shingles could be prevented, postherpetic neuralgia
could be completely avoided.
Recently, Merck has tested a new vaccine (Zostavax) against shingles.
This vaccine is a more potent version of the chickenpox vaccine.
Evidence indicates that the vaccine reduced the incidence of
shingles by 51 percent. Additionally, the vaccine reduced the
incidence of PHN by two-thirds compared to placebo. However, the
vaccine's protective effects diminished over the three years that
most patients were followed. In
December 2005, an FDA advisory committee unanimously agreed that
the vaccine is safe and effective for persons over 60 years
was followed on 26 May 2006 by the FDA formally approving the use
of the vaccine for that same age group. Further
studies may demonstrate if there is benefit in patients 50–59 years
old and if a booster dose is recommended.
Bowsher, David, MD, ScD, PhD. "Treating shingles with
tricyclic antidepressants to lessen the risk of PHN". The
Center for Shingles and Postherpetic Neuralgia. http://shingles.mgh.harvard.edu/tricyclics.htm. Retrieved
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"Merck Zostavax Shingles
Vaccine Decreases In Efficacy Over Three-Year Period, FDA
Says". FDA Advisory Committee. 2005-12-15. http://www.fdaadvisorycommittee.com/FDC/AdvisoryCommittee/Committees/Vaccines+and+Related+Biological+Products/121505_Zostavax/121505_ZostavaxP.htm. Retrieved
"Merck Zostavax Shingles
Vaccine Safe and Effective For Adults Over 60, Committee Says".
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- Commentary at
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