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CUSHING’S SYNDROME
THE
“COMMON” DRUG THERAPIES
This month my article will focus mainly on the “common
drug therapies” used for treating a dog with Cushing’s Syndrome.
Before starting Boomer on a course of treatment, I did extensive research
into each drug that was available, the protocol for administration, the side
effects, the warnings, and the dangers that sometimes accompany
“chemotherapy”.
Below is what I discovered:
L-Deprenyl
(Anipryl)
This drug is sometimes considered
first in the treatment of PD Cushing’s. It
has been show to only work for PD Cushing’s cases.
It is used for Parkinson’s disease in people and is also used to treat
canine cognitive dysfunctions (CD). In
fact, a few of my friends had used this drug on their older goldens with canine
cognitive dysfunction and did have success.
Another nice thing about this drug is that if your dog is elderly when
diagnosed with Cushing’s, you may be able to successfully treat two diseases
with ONE medication!!
Anipryl affects the hypothalamus
and its interaction with the pituitary gland in relation to a chemical called
dopamine. There are minimal side
effects. Many dog owners who
belonged to one of the various Cushing’s listservs that I had joined when
Boomer was first diagnosed substantiated low to no side effects.
Unlike the other drugs used to treat PD Cushing’s, ACTH testing is of
no value to monitor effectiveness. The
drug does not act on either the pituitary or the adrenal gland.
The recommended dosage is given
daily for 2 months. If the symptoms
don’t diminish within that time period, the dose is increased.
The majority of PD Cushing’s dogs will show improvement within the
first 2 months. If after an increase
in dosage, there is still no improvement, then other illnesses need to be
considered. If other
illnesses/diseases are not found, then other drug therapy should be instituted.
A word of caution:
Anipryl should not be used if your dog is being treated for Demodex with
Mitaban or with antidepressant medications or Prozac.
The most
commonly used drug therapy used in the
United States
for dogs diagnosed with Cushing’s Syndrome is:
Mitotane (o,p’-DDD)
The trade name or name by which
it is most familiar is Lysodren. Lysodren
works to control Cushing’s by selectively destroying the zona fasciculate and reticularis, effectively
limiting the amount of cortisol that these areas of the adrenal gland can
secrete. It should be administered
with meals to enhance its absorption. This drug requires what is known as a
“loading dose” for 7 – 10 days.
Side effects are NOT uncommon and
may include:
·
lethargy
·
vomiting
·
diarrhea
·
anorexia (lack of
appetite)
·
weakness
·
ataxia (incoordination)
The side effects are due to the
cortisol level being reduced BELOW the normal levels.
Even when the cortisol levels do not go below “normal levels”, the
rapid decease in the once “elevated cortisol levels” to the “normal
range” can still cause
the symptoms listed above.
It is imperative that you keep an
eye on your dog for any of the side effects mentioned, when using the Mitotane
therapy. If
any of them should occur it is extremely important to immediately stop
administering the medication and get in touch with your veterinarian. Most vets
will also prescribe prednisone to have on hand at home, should the side effects
be significant.
After the 7-10 days of
“loading”, the cortisol
levels are assessed with the ACTH stimulation test.
You will be instructed to not give your pet any supplemental cortisone on
the day of testing. If the pre and
post cortisol levels come in “normal”, then a “weekly” Mitotane
maintenance dose is prescribed and occasional ACTH stimulation tests are
recommended by most veterinarians to ensure the cortisol levels are staying
within the “normal” range.
Unfortunately, two long-term
effects can occur while on Mitotane maintenance therapy:
The drug can be so effective that the adrenal glands
stop producing enough cortisol for normal physiology.
This is call iatrogenic hypoadrenocorticism.
When this occurs, all Mitotane therapy is stopped and supplemental
prednisone is administered. This
side effect can be permanent and you’re your dog will need to be on
supplemental prednisone the rest of his or her life.
The second side effect is for a
“relapse” to occur within 12 months, even while on the maintenance therapy.
Another “loading” dose is required, then a conversion to a
maintenance dose when it is ascertained that the cortisol levels are again
normal through the ACTH stimulation test.
Because of the side effects, the
importance of continual monitoring of your dog must be emphasized!
This means close observation at home for clinical signs and ACTH
stimulation tests every 3 to 6months.
Ketaconazole
Routinely used to control fungal
infections. This drug inhibits the
production of cortisol in dogs and humans by preventing enzyme pathways from
functioning properly. It is
prescribed for both PD and AT Cushing’s. It is
not as commonly prescribed as the previous 2 drugs.
A test dose is initially given
with the owner told to watch for anorexia and/or vomiting.
If tolerated, a “loading”
dose is given for 7 – 10 days, after which an ACTH Stimulation test is
performed. If the cortisol is
determined to be in the “normal” range, the drug is given every 12 hours for
the rest of the dog’s life.
I was not able to find much
information on side effects, as this drug is not widely used in the
United States
.
Surgery
Surgery to remove both adrenal
glands can also be used. It is an
involved endeavor and should be performed by a specialized surgical hospital.
Post operative
complications are common, and these dogs need lifetime prednisone replacement
therapy. As a result, this treatment
is not commonly utilized.
Radiation
If after the initiation of the above therapies, symptoms of PD
Cushing’s reoccur, this might be an indication of a large pituitary tumor.
An MRI might be recommended to identify this type of tumor and radiation
may be recommended to prevent further progression of symptoms.
Unfortunately, radiation specialty centers that can perform this
procedure are not widely available.
Iatrogenic Cushing’s (a/k/a drug induced)
This type of Cushing’s is the
easiest to treat! No medication is
necessary; however, the “removal” of one is!
In most cases the elimination of exogenous cortisone will return your dog
to normal function. However, this
may take several months and some of the skin changes associated with Cushing’s
may take longer. Some skin
conditions may never correct themselves or return to a total normal state.
In some cases, your veterinarian may use a decreasing dose of
supplemental prednisone for several weeks to give the adrenal glands time to
resume to normal cortisol production.
Adrenal Tumor (AT)
Should your dog be diagnosed with
AT Cushing’s, most likely he/she will require surgery.
The surgery to remove the cancerous adrenal gland is called an
adrenalectomy. It is a specialized
surgery that is not routinely performed. Post
operative complications may occur and are somewhat common.
Due to the remaining adrenal
gland being atrophied, the dog will need to be supplemented with prednisone
until that gland returns to normal function.
ACTH stimulation tests are done every few months to determine when the
gland is functioning normally again. It
can take up to 12 months for this gland to return to its normal functioning
process.
It should also be noted that
adrenal tumors can be treated with Mitotane at high doses and for a long period
of time. Side effects are again
common at this dose and, relapses may and can occur.
Dogs will also need to be supplemented with prednisone for the rest of
their lives.
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Due to the length of this
month’s article, I have decided to wait until next month to discuss the drug
therapy I am using to treat Boomer. It
deserves the entire article!! Let’s
just say…I am extremely pleased with its results…and so is Boomer!!
As always, the above information is based on my personal research and
first hand experience with my golden retrievers.
My reference for the medical/technical information for this article is: http://www.lbah.com/Canine/cushings.htm.
I can be reached at boomer@trianglenet.net
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