Idiopathic epilepsy: Seize the day (and save the pooch)

Getty imagesEpileptic seizures are a common disorder in dogs seen in general veterinary practice. The prognosis often depends on the quality of life for the dog and for the owner, so it's important to balance the treatment with the pet owners' budget, stress level and perception of the dog's quality of life. Veterinarians are left with a lack of uniform guidelines to treat epilepsy.

The International Veterinary Epilepsy Task Force published consensus statements to help veterinarians choose appropriate monotherapy for idiopathic epilepsy. Here's a summary of key points.

When to start treatment

Initiation of treatment is based on a number of factors, but the panel recommends starting treatment when:

1. Identifiable structural lesions are present or the patient has a prior history of brain disease or injury

2. Acute repetitive seizures are present lasting longer than five minutes or more than three generalized seizures occur within a 24-hour period

3. Two or more seizure events have occurred within a six-month period

4. Prolonged or severe postictal periods are affecting the patient's quality of life.

What treatment to reach for

No single drug will effectively treat every patient, but the panel looked at several options.

• Phenobarbital. This drug is very bioavailable has the longest history of use in veterinary medicine. Phenobarbital is relatively inexpensive and well-tolerated, with a cumulative success rate of improving seizure control at 82%.1-5

• Potassium bromide. Potassium bromide has not been evaluated extensively for use as monotherapy, but one study found that 73.9% of dogs had a more than 50% reduction in seizures and that 52% were seizure-free during the six-month treatment period.4 It is generally considered safe, but effectiveness has been more often evaluated in combination drug with other therapies.

• Primidone. The panel found that there is no advantage to using this drug over phenobarbital to control seizures in most dogs.

• Imepitoin. This drug is currently unavailable in the United States, but several studies have identified consistent efficacy for the control of seizures in dogs.

• Levetiracetam and zonisamide. Neither of these drugs have been extensively studied for safety and efficacy.

Risks of treatment

Four categories of adverse effects have been established.

Type 1: Predictable effects (polydipsia, polyphagia and lethargy)

Type 2: Unpredictable and potentially life-threatening effects

Type 3: Cumulative with long-term treatment and potentially life-threatening effects

Type 4: Delayed and life-threatening, carcinogenic or teratogenic effects

Phenobarbital is generally well-tolerated. Sometimes polydipsia and polyphagia can affect a pet's bond with its owners. Thyroxine concentrations may be low in dogs receiving phenobarbital, causing a mistaken diagnosis of hypothyroidism. Drug-induced hepatotoxicosis is a rare but potentially life-threatening complication. Perform a serum chemistry profile in patients receiving phenobarbital every six months, followed by a bile acid assay if altered liver function is suspected. There are no type four adverse effects noted for this drug in dogs.

Potassium bromide is generally well-tolerated in dogs, with occasional type 1 complications such as polydipsia, polyphagia and lethargy. Type 2 effects can come from gastric irritation. Type 3 effects are rare, but care should be taken when using this drug in patients with renal compromise.

Primidone has similar type 1 and type 2 effects to phenobarbital, with type 3 hepatic enzyme activity increases noted slightly more often than with phenobarbital. Similar hepatic assays should be performed.

Refractory cases and concluding thoughts

Sometimes seizures are considered refractory, and a second medication should be considered. Strict criteria for such decision-making are lacking in veterinary medicine. Alternative therapies were considered by the panel, but none were found to be extremely effective.

In the end, the decision falls to the general practitioner, who must balance the financial burden and stress on the family with the dog's quality of life.

Podell M, Volk HA, Berendt M, et al. 2015 ACVIM Small Animal Consensus Statement on Seizure Management in Dogs. J Vet Intern Med 2016;30:477-490.

Link to article: http://onlinelibrary.wiley.com/doi/10.1111/jvim.13841/epdf

References

1. Loscher W, Potschka H, Rieck S, et al. Anticonvulsant e?cacy of the low-a?nity partial benzodiazepine receptor agonist ELB 138 in a dog seizure model and in epileptic dogs with spontaneously recurrent seizures. Epilepsia 2004;45:1228-1239.

2. Rieck S, Rundfeldt C, Tipold A. Anticonvulsant activity and tolerance of ELB138 in dogs with epilepsy: a clinical pilot study. Vet J 2006;172:86-95.

3. Morton DJ, Honhold N. E?ectiveness of a therapeutic drug monitoring service as an aid to the control of canine seizures. Vet Rec 1988;122:346–349.

4. Boothe DM, Dewey C, Carpenter DM. Comparison of phenobarbital with bromide as a ?rst-choice antiepileptic drug for treatment of epilepsy in dogs. J Am Vet Med Assoc 2012;240:1073-1083.

5. Tipold A, Keefe TJ, Loscher W, et al. Clinical e?cacy and safety of imepitoin in comparison with phenobarbital for the control of idiopathic epilepsy in dogs. J Vet Pharmacol Ther 2015;38:160–168.