Dalmatian Club of America
Anti Epileptic
Drugs
Phenobarbital (PB)
Clinical reports indicate that 60 to 80% of epileptic
dogs can be controlled effectively with only PB. It is relatively inexpensive,
fairly easy to maintain PB serum levels with 2 or 3 times a day daily dosing
and has few side effects. You may be afraid to use PB because of liver
damage however in the beginning it is very important to get the seizures
under control When PB is used properly, PB serum levels monitored as well
as testing liver functions, the risk of liver disease is very low. Each
dog is different, so is their ability to metabolize medications.
The only way to determine if your dog is getting the proper
dosage is to monitor the PB serum concentrations (levels). This is done
with a blood test. The first level is usually taken 2 weeks after initially
starting PB therapy.
Based on the level results and also on how well the seizures
are controlled, the dosage can be adjusted. If the PB blood serum level
results come back and are not what you expected and there is no known reason
for them to be ' off ', ask to have the test re-run. Levels should be taken
at least twice a year, It is very important to ask the vet to run
a full panel of Liver Function tests to see if the liver is becoming compromised
by the PB using the following tests ALT (SGPT), AST (SGOT), GGT, and
Alkaline Phosphatase. If there are signs of early liver damage, Milk
Thistle can often help slow down or reverse the problem. Give no more than
a 1/4 of the adult human dose listed on the bottle daily and only
if liver damage has occurred.
When the lab sends your veterinarian the results from
a PB serum level test, they will note the range that the lab uses. One
suggested range is 20-35 ug/ml (86-150umol/l in countries that use micromoles),
another is 15-45 ug/ml and yet another is 15-40 ug/ml. In general the low
level of the therapeutic range means that 50% of the dogs at the low level
will exhibit some benefit (i.e.: seizure control) from the PB. Likewise,
50% of the dogs that are at the upper limit will NOT show signs of PB toxicity.
As you can see, these lower and upper therapeutic ranges are a little vague.
Therefore it is just as important to take into consideration your dog's
seizure control and side effects rather than just relying on the numbers.
In the beginning it is important to test the trough level.
A trough level represents the PB serum concentration when it is at it's
lowest in the dog's system. If this level is too low, your dog could have
a seizure. Therefore it is important in the beginning that this level is
within therapeutic range. Some suggest that a minimum trough level is 20.
After your dog has been on PB and steady-state levels
have been reached, a PB peak level can be taken. While the trough level
is taken just before the next dosage is due, the peak level is taken anywhere
from 4-6 hours (some say 4-8 hours) after PB dosage. Also if your dog has
been given food, the food can delay the 'peak' period by several hours.
So as you can see, determining the 'peak' time is not exactly precise.
The peak level represents the maximum amount of PB in the system and is
important for determining whether your dog might be reaching toxic levels.
There are other signs of toxicity too – ataxia (muscle weakness in the
hindquarters) and the beginning of liver disease are two of them.
If you notice that your dog is exhibiting a behavior that
results in a seizure, you can increase the PB dosage for a short period
of time until you are sure that the potential for having a seizure is over.
Then you can return to the normal dosage. If you think a seizure might
be brought on by stress (like company, visiting the vet or dog groomer),
you could try using Bachs Flower Essence Rescue Remedy. Rescue Remedy is
also very useful for helping with the post ictal (after effects) of a seizure.
In many cases it cuts down the wandering and pacing which so often causes
more distress for the owner than the seizure itself, RR can be bought in
any health food store. Put a dropper full in the dog’s mouth between the
cheek and the gum. Be careful however not to let the dog bite down on the
dropper as it is made of glass.
Also valuable to reduce the post ictal phase are small
amounts of Breyers Natural Vanilla Ice Cream and a full meal.
Potassium & Sodium Bromide (KBr & NBr)
Bromide therapy should be considered for dogs whose seizures
are considered refractory (not controlled by another AED (anti epilepsy
drug)). For those dogs, using KBr & PB concomitantly (together) has
produced some very promising results. One study reported that dogs that
were refractory to PB, 86% of them had improved seizure control and 26%
of the 86% became totally seizure free when adding Potassium Bromide (KBr)
Two very important reasons for considering bromide therapy
are: it is effective in controlling cluster seizures, and it is not processed
by the liver
Bromide should be given with food and not on an empty
stomach. It can simply be squirted on your dog's food or on a small piece
of bread and given to your dog.
IMPORTANT
The chloride content of your dog’s food can affect
the absorption of bromide. Chloride affects the elimination of bromide;
thus increases in dietary chloride will decrease bromide levels. In one
study, increasing the chloride content from that of most commercial foods
(0.4% chloride on dry matter basis) to that of a high chloride diet (1.3%,
comparable to some prescription diets), a three-fold increase, increased
the necessary dose of bromide by almost 100%. The food's chloride content
is normally not listed on the food label. Therefore, it might be necessary
to contact the dog food manufacturer to obtain this information. Once bromide
therapy has been started, it is suggested that the dog's diet not be changed.
But if you must, you need to take into consideration the difference in
the chloride content between the two foods and discuss this with your veterinarian.
Bromide is generally well tolerated in dogs. However,
some of the side effects are the same as with PB. That is sedation, ataxia,
increased hunger, and the 3 -P's: polydipsia (excessive thirst), polyphagia
(excessive hunger) & polyuria (excessive urination). In some cases,
dogs can develop a skin rash or itchy skin. As with other AEDs, these side
effects can diminish with time. If using a loading dose, these side effects
will be more noticeable. In many cases, reducing the PB or bromide can
reduce or eliminate these symptoms. If a dog does show signs of toxicity,
many times lowering the dosage and then gradually increasing it back up
over time solves the problem. Again be sure to discuss this with your veterinarian.
Potassium bromide is preferable in dogs that need
to have their sodium restricted (e.g. dogs with certain heart diseases,
high blood pressure). Sodium bromide seems to be less irritating
to the stomach and is often used in dogs that suffer from nausea/vomiting
with the potassium salt. Sodium bromide is also preferable in dogs
with certain diseases (e.g. primary hypoadrenocorticism) that cannot tolerate
excess potassium. Also, some dogs object less to the taste of sodium
bromide. Except for the gastrointestinal side effects (which are due to
the potassium) the side effects and the effectiveness of these two preparations
are identical.
Bromide is a salt and is available in capsule or liquid
form A bromide solution is prepared by dissolving bromide in double-distilled
water. A compounding pharmacy can prepare liquid bromide in any convenient
concentration (strength) you need. This could be 100 mg/ml, 200 mg/ml,
250 mg/ml, 300 mg/ml or higher. The higher the concentration, the saltier
the taste. You usually don't want to go much higher than 500 mg/ml. Many
people have found that the solution works better as it is easy to adjust
the dose if side effects appear.
When starting bromide at the maintenance dose, it takes
a couple of months or so to obtain therapeutic blood levels. A much higher,
initial "loading" dose is sometimes used to immediately raise the blood
level into the therapeutic range. This may be preferable when:
-
The dog is suffering frequent seizures, which need to be
controlled quickly, or
-
When another anti-seizure drug, such as Phenobarbital, must
be stopped quickly (for example, due to the development of liver disease).
Each dog is different, so is their ability to metabolize
medications. The only way to determine if your dog is receiving the proper
dosage is to monitor the bromide serum concentrations (levels). This is
done with a blood test.
The target range for dogs taking bromide and Phenobarbital
is usually around 100-200 mg/dl. This is equivalent to 1-2 mg/ml or 1000-2000
ug/ml. Dogs taking bromide alone may require levels as high as 300 mg/dl.
A few dogs can tolerate blood levels over 400 mg/dl with no side effects,
but most dogs show some signs of toxicity at levels above 300 mg/dl.
As you can see, the effects of bromide blood levels vary
quite a bit in different dogs. In general the low level of the therapeutic
range means that 50% of the dogs at the low level will exhibit some benefit
(i.e.: seizure control) from the bromide. Likewise, 50% of the dogs that
are at the upper limit will NOT show signs of bromide toxicity. As you
can see, these lower and upper therapeutic ranges are a little vague. Therefore
it is just as important to take into consideration your dog's seizure control
and side effects rather than just relying on the numbers.
Finally please be aware that bromide therapy is no
longer thought of as a last ditch effort for seizure control.
As an add on AED or used alone KBr could just save your dogs life.
Gabapentin
Gabapentin is one of the newer AEDs (anti epilepsy drugs)
that has become available for humans and canines within the last few years,
after some 15 years of research. It offers some exciting potential
for use in dogs. It is most often used as a secondary (or add-on) drug
to help treat seizures that cannot be controlled by other AEDs alone. Also,
it is recommended that if a dog is on Phenobarbital and potassium or sodium
bromide, blood serum values be within therapeutic range before starting
on Gabapentin therapy. Gabapentin has been recommended by board certified
neurologists for seizure control.
A major advantage to this drug is that it is only partially
metabolized by the liver in dogs unlike some of the other AEDs. It also
can be used in combination with liver-metabolized anticonvulsants (i.e
Phenobarbital).
Gabapentin really seems to work as an add on AED.
Dogs that were given Gabapentin were not totally seizure-free, but improved
significantly. Gabapentin must also be given at least three times a day
to have effective serum drug concentrations.
However, Gabapentin is rather expensive. The dosage for
Gabapentin is 7 to 15mg/kg every 8hrs. It would cost $75 a month for a
60lb dog starting at 7mg/kg. The basis for this cost is 42 cents per 100mg
of Gabapentin. By comparison, it would cost $87 a month for a 90lb dog
starting at 7mg/kg. The basis for this cost is 97 cents per 300mg of Gabapentin.
Gabapentin comes in 100mg, 300mg & 400mg capsules. A good source to
obtain this drug can be found on the Compounding Pharmacy page of the Epil-K9
Website http://www.canine-epilepsy.com
Please
Note:
The opinion(s) expressed
above is/are for informational purposes only.
Suggestions and advice
offered, are not be misconstrued as an alternative to personal and professional
veterinary care. Please contact your veterinarian to discuss any changes
in your dogs medication or care.
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