CPD ACCREDITED ARTICLE
Optimal Management of
Canine Seizures
Extracts from the 2015 ACVIM Consensus Statement on Seizure Management in Dogs
By : Dr LL van der Merwe BVSc MMed Vet ( Med )
Seizures are common in dogs and are characterised by a wide variety of clinical signs / presentations . Epilepsy is a syndrome and not a diagnosis as such , a specific diagnosis as to the cause of the seizure is not made in the majority of cases due to a variety of reason . In epilepsy , survivability depends more on the quality of life and financial constraints than the disease itself . The definition of successful treatment is a decrease in seizure episodes by at least 50 %. The majority of patients are easily managed if a few basic guidelines are adhered to .
PHENOBARBITONE
Phenobarbitone ( PB ) is considered an effective monotherapy in 60 – 80 % of dogs . When it fails it is more often due to inappropriate use of the drug than resistance to the medication . The control of seizures and minimisation of side effects using PB are correlated more closely with serum concentrations than with the dose administered .
Typically , consistent administration of a medication for a period of four to five half-lives is required to reach a steady state . The relatively long elimination half- life of PB ( 50 – 96 hrs ) limits fluctuations in blood levels however , once on treatment , the elimination half-life becomes more variable , ranging from 20 – 140 hours .
Phenobarbitone induces drug metabolising pathways in the liver , including its own p450 cytochrome enzyme and thus elimination becomes more rapid with long term administration . There is no predictability to this pattern , so we need to monitor serum drug levels to determine if the dosage of PB is sufficient to reach therapeutic drug levels .
The aim should be to reach mid therapeutic doses which could be classified as about 26 – 35ug / ml ( range 15 – 45ug / ml ) - this generally seems to require a higher starting dose than the traditional 2-5mg / kg / day . I , however prefer to titrate upwards from about 5mg / kg per day ( 2 -3 mg per kg BID )
CONSENSUS RECOMMENDATIONS
When should treatment be started ? This decision to start treatment is based on aetiology , seizure type , risk of recurrence and tolerability and adverse effects of medication . In people , current or previously diagnosed cerebral lesions or trauma predisposes to recurrence . In people there is also overwhelming evidence that treatment should not be instituted after one ( unprovoked ) seizure event . There is also evidence that the earlier treatment is started , the better the potential of seizure control . So a balance must be created .
ACVIM panel recommendations to initiate treatment are : i . Identifiable structural brain lesion or prior history of brain disease or trauma ii . Acute repetitive seizures ( ≥3 generalised seizures within
24hrs ) or status epilepticus ( ≥5 min of seizuring ) iii . ≥ 2 seizure events in a 6 month period iv . Prolonged , severe or unusual post-ictal periods
Which treatment should be used first ? As Monotherapy : 1 . Phenobarbitone - Highly recommended , based on level 1 data ( designed and controlled trials ). In 5 studies evaluating a total of 289 dogs for 5 - 32 months , the cumulative success (> 50 % reduction in seizure events ) was 82 % with a cumulative seizure free rate of 31 % and a failure rate of 15 %.
2 . Imepitoin ( Pexion ®) - Highly recommended-based on level 1 data ( designed and controlled trials ). In a multicentre study imepitoin was shown to be as effective as phenobarbitone in 226 epileptic dogs in a randomised blinded parallel group design with a lower frequency of side effects ( ataxia , sleepiness , increased appetite and polydipsia ) compared to the phenobarbitone group .
3 . Potassium Bromide - Moderately recommended and likely to be effective - based on level 2 data ( case controlled series ). A single study evaluating monotherapy showed an efficacy of 73.9 % patients showing > 50 % seizure reduction and 53 % seizure free in a 6 month period . vet360
Issue 06 | FEBRUARY 2017 | 6