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Vancouver,
B.C.— Patients who suffer from the intractable, disabling
pain of postherpetic neuralgia (PHN) can get quick relief from a
single injection of Botulinum toxin A, Kevin Smith, MD, told participants
at Dermatology Update.
“This is a good example of how cosmetic dermatology gives back
to general dermatology and general medicine,” said Dr. Smith,
a Niagara Falls dermatologist.
He described a 73-year-old female patient with a three-year history
of pain in the right forehead and scalp, in a V1 distribution. She
identified 10 points in the involved area. After obtaining informed
consent, and in particular pointing out that some brow ptosis would
certainly occur following the procedure, Dr. Smith injected each
of the 10 sites which the patient identified as painful in the area
of PHN with five units of BOTOX THERAPEUTIC™, reconstituted
at 100 units/mL.
“She experienced almost complete pain relief within one week
and remained pain free at four months of follow-up.”
An 84-year-old male with a three-year history of intractable PHN
in the left forehead (V1 distribution) received six injections of
7.5 units of BOTOX per site in painful areas he identified in the
left V1 distribution. He had considerable improvement in most of
the V1 distribution within a week, except in the area of a scar
where a large basal cell carcinoma had been excised and covered
with a flap several years before. BOTOX treatment was very well
tolerated, apart from the expected degree of brow ptosis that responded
adequately, but not completely, to Iopidine (apraclonidine) 0.5%
eyedrops tid prn.
“The area of persistent PHN is now restricted to the area of
the surgical scar on the left forehead, and the other areas are
almost completely asymptomatic. It’s been suggested that maybe
there’s a neuroma or something else contributing to the pain
in the surgical scar,” Dr. Smith said.
“Interestingly, his brow ptosis responded very well to Iopidine.
Dr. Jean Carruthers recently suggested that it can also be used
for brow ptosis in some cases, and, lo and behold, this patient’s
brow ptosis got better within about one minute.”
Dr. Smith credited Drs. Arnold Klein of Beverley Hills and Rick
Glogau of San Francisco for making the first (and so far, unpublished)
observations about the utility of BOTOX for PHN.
Technique
The areas of maximal discomfort in the affected area are identified
by the patient making an index fingernail mark at the exact sites,
which are then marked with a fluorescent marker. The involved area
with the marks is photographed, and the sites indicated by the patient
are injected intradermally (where the majority of the nerve endings
are located). Intradermal injection may also reduce unwanted muscle
weakness, Dr. Smith said. Photography helps the dermatologist find
the previous injection sites to either replicate a treatment or
avoid doing something that may cause a problem.
Asked how BOTOX compares with gabapentin (Neurontin), Dr. Smith
said gabapentin floods the whole body with drug and can produce
a variety of side effects, including increased risk of falling in
the elderly, whereas BOTOX treatment is precisely localized to the
treated area.
“T the extent that BOTOX works for PHN, it may turn out to
be a lots safer, more effictive, and less expensive than treatments
like gabapentin. Only time will tell,” Dr. Smith said.
BOTOX may act in PHN and other painful conditions by modulating
the release of the neuropeptides Substance-P and calcitonin gene-related
peptide, and perhaps even by retrograde axonal transport along C-fibres,
with effects on central glutamate release, he said. Dose ranging
studies may be useful to optimize the ratio between pain reduction
and unwanted muscle relaxation, he added.
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