WSAVA Nov 2021 Proceedings - Flipbook - Page 29
- Abnormal neurological examination
cause of the seizures
- Seizures starting outside the 6 month to 6 year age range
- Post-ictal signs are objectionable (e.g. aggression)
- Abnormal behaviour in between the seizures
Phenobarbitone (2 to 3 mg/kg q.12 hours orally) is the first choice of
many clinicians for dogs and cats with idiopathic epilepsy. In dogs,
repeated phenobarbitone administrations are known to alter estimated
steady state serum concentration as a consequence of enzyme induction
(cytochrome P450 induction). This results in the need to regularly monitor
serum phenobarbitone level and progressively increase oral dosage with
time in order to maintain steady state therapeutic level. This phenomenon
of enzyme induction following repeat administration of phenobarbitone
is negligible in cats. Recommended therapeutic range in dogs is 20 to 35
ug/ml. This therapeutic range is only an indication in the adaptation of the
oral dosage. Most dogs will “respond” (reduction in frequency, intensity
and severity of the seizures with minimal side effects) with serum level
within this range. However, some dogs might need to be in the upper limit
of this range while others might need to be below the lower limit. Imepitoin suppresses seizure activity in a similar manner to other AEDs. The
recommended dose is 10-30 mg/kg twice daily. The starting dose is usually 10mg/kg twice daily to control seizure ie a 30kg Golden Retriever will
receive 300mg twice daily. They do include PuPd, polyphagia, ataxia, restlessness and sedation. They can also cause gastrointestinal side effects.
Blood tests are not required to check on this drug. This drug tends to be
most effective in dogs with few seizures and it is not often recommended
on its own where multiple seizures are seen, or where epilepsy is proving
progressive. An animal is defined as refractory to anti-epileptic treatment
when the patient quality of life is compromised by frequent and severe
seizures despite appropriate drug therapy (serum level in the high end of
the therapeutic range) or side effects of the medication. The incidence of
refractory epilepsy is unknown in dogs but could be as high as 25% of epileptic patient. Therapeutic options in refractory epilepsy consist mainly in
adding (or replacing for dogs or cats with side effect of phenobarbitone)
a second anti-epileptic drug. Second anti-epileptic drugs currently used
in dogs include bromide (30 mg/kg q.24 hours orally), levetiracetam (10
to 30 mg/kg q.8 to 12 hours orally), topiramate (2 to 10 mg/kg q.12 hours
orally) and zonisamide (5 to 10 mg/kg q.24 hours o
- Loss of learned behaviour (e.g. loss of toilet training)
- Circling/pacing
- Visual impairment/bumping into things
- Does not respond to appropriate anti-epileptic drug therapy
AIMS OF ANTI-EPILEPTIC TREATMENT
The aim of any anti-epileptic treatment is to “control” the seizures by
reducing their frequency, intensity and severity with minimum side effects
while maximizing the owner’s and dog’s quality of life. Owners should
be appropriately advised to ensure that their expectations are realistic
from the outset. Unless idiopathic or cryptogenic epilepsy is considered
to be the primary differential diagnosis for the seizure activity, specific
treatment of the underlying cause is essential and the success of this will
determine the need for symptomatic seizure therapy.
IMPORTANT MESSAGES TO PROVIDE TO THE OWNER OF AN
EPILEPTIC ANIMAL
- The therapy for epileptic seizures does not aim at curing the epilepsy but
aims at “controlling” it.
- Therapy for epileptic seizures may have side effects that in rare occasion
can be worse than the seizures themselves.
- Mild side effects are common when first starting treatment with anti-epileptic drugs.
- Therapeutic effects and side effects are related to the serum levels and
not the oral dosage of the anti-epileptic drug.
- Skipping doses or stopping drugs abruptly can precipitate seizures
(dependency effect).
- Seizure control may not take immediate effect as a steady serum state is
only reached after 5 elimination half-lives (around 2-weeks in phenobarbitone and up to 3-months in potassium bromide).
- Clients must keep accurate record of the date of any witnessed or suspected seizures and must be willing to bring their dog or cat in for periodic
examination.
- Clients should seek immediate veterinary care for any seizure lasting longer than 10 minutes or for clusters of seizures without recovery to normal
between the seizure episodes.
- Clients should not alter the treatment without veterinary advice.
WHEN TO START ANTI-EPILEPTIC TREATMENT
The decision of when to start anti-epileptic treatment is still a subject of
controversy. Dogs with a single seizure or isolated seizures separated
by long periods of time (more than one month) do not require treatment.
Treatment is indicated when:
- The animal has a very severe seizure or clusters of seizures, irrespective
of the frequency of the seizures or seizure clusters
- Seizures occur more than once a month and/or the owner objects to their
frequency
- Seizures are becoming more frequent or more severe
- An underlying progressive intracranial disorder has been identified as the
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