It is important to understand the likely outcome once a dog has been diagnosed with epilepsy. The treatment goals will vary between patient’s and we must also not forget that the majority of patients with epilepsy have a progressive course and so regardless of what is done it is likely the seizure frequency will increase slowly over time.
Will the dog get better?
An epileptic animal is born with the condition and cannot be cured. It is the goal of treatment to control their seizures. While anti-epileptic drugs can eliminate seizures in some animals, for the majority of pets, treatment is considered successful if seizures have been reduced by 50% or more with few side effects. If a dog has epilepsy, despite receiving treatment, he or she may still have some seizures. In some dogs, despite adequate therapy, seizure control is not always possible.
When should treatment be started?
Epilepsy treatment is likely to continue for the rest of the patient’s life once it is started. As some dogs only have a single seizure episode, it is not sensible to put them all on permanent treatment from the beginning (since many will never have another seizure).
It is possible to divide thinking into two camps. It may not be feasible to treat every dog that seizures, since most will only have one seizure episode in their lives. When a dog develops recurrent seizures (i.e. after the second episode), the first school of thought recommends treating it as soon as possible. One study in dogs shows that early treatment for epilepsy in dogs results in better long-term control of seizures than animals that are allowed to have numerous seizures before treatment begins.
In the second school, antiepileptic therapy must be balanced with the negative effects of the medication and the demands on the owner.
The following would be a reasonable guide to starting treatment for epilepsy in dogs:
- The owner finds the frequency distressing or the patient has more than one seizure a month.
- There is a very severe seizure or cluster of seizures, regardless of their frequency.
- There is an increase in the frequency or severity of their seizures.
- Seizures have been linked to an underlying brain disease.
What drugs are used for the treatment of epilepsy?
The majority of drugs used in epilepsy in people are toxic to pets or are removed from the body so quickly that seizures cannot be effectively controlled. Veterinary-licensed drugs such as phenobarbital or imepitoin (Pexion®) are usually prescribed as the first line of treatment in dogs. In terms of seizure control, these two drugs are similar, with pros and cons for each. The frequency of seizures, the presence of clusters (more than one seizure in a day), and the need for regular blood tests for drug monitoring must be considered. It is not recommended to use diazepam as a maintenance treatment for epilepsy in dogs because its duration of action is too short.
What blood tests are required during treatment?
When using phenobarbital, blood tests are required regularly, but not when using imepitoin.
Different animals respond differently to anti-epileptic treatment. Imepitoin is usually started at a low dose and increased until it is effective (e.g., reduced frequency of seizures with minimal side effects).
The dosage of phenobarbital is not as important as the level of the drug in the body when using the drug. Drug levels in the blood determine both the therapeutic and toxic effects of a drug. It is possible to measure phenobarbital blood levels to ensure that they are within a certain range (therapeutic range) that controls seizures with minimal side effects. When the concentration is not within this range (too low or too high), the quantity of tablet should be adjusted and the concentration re-checked after a few weeks. It is extremely variable from animal to animal how well they respond to epilepsy treatment. Therapeutic effects will be experienced by some at the low end of the therapeutic range, while others at the high end. In other words, checking the concentrations are within the therapeutic range is not enough; you must also consider what effects (beneficial or undesirable) it will have on the animals.
Moreover, the concentration of phenobarbital in dogs tends to decrease with time (more or less quickly depending on the dog). In order to maintain the same blood concentration, the tablet quantity will need to be increased. This does not mean the animal is more likely to suffer side effects since the inefficiency, therapeutic, and toxic effects are related to the amount of drug in the blood.
When should blood samples be taken?
A blood test should be performed to measure the levels of phenobarbital in the blood:
- Approximately 2 weeks after starting the treatment or changing the dose.
- If seizures are occurring more frequently.
- Every 3 to 6 months to check that blood concentration does not drift out of the intended range.
- Whenever there is a suspicion of side effects related to drugs.
What are the side effects of anti-epileptic drugs?
Epileptic drugs can sometimes have worse side effects than the seizures themselves. The first few days of treatment (or increasing the dosage) are often accompanied by mild side effects. Phenobarbital can cause increased thirst and appetite, more frequent urination, mild sedation and mild wobbliness in the back legs. Phenobarbital may also cause liver toxicity, low platelet counts, low red blood cell counts, and low white blood cell counts. To monitor for such potential side-effects, complete blood profiles (liver function tests and haematology) are recommended three times a year in the first year, then every six months thereafter.
The dose of imepitoin given to dogs is generally well tolerated and most dogs do not suffer any ill effects. Sedation, appetite, drinking, and wobbliness are occasionally observed. Diarrhoea and vomiting have been reported in some dogs, but they are rare.
Tell me more about Phenobarbital
An epileptic seizure can be prevented by taking phenobarbital, a barbiturate medication. ‘Epiphen’ and ‘Soliphen’ are common trade names. It has a long elimination half-life in dogs, which means it stays in the blood stream for a long time. In dogs, it is the most commonly used antiepileptic drug (AED). It is recommended that the starting dose be between 2 and 3 mg/kg given twice a day. In general, we recommend checking phenobarbital serum concentrations (blood tests) after 2 weeks, 3 months, 6 months, and then every 12 months thereafter. Phenobarbital levels should be checked 2 weeks after changing dosages, or in the event of clinical signs of toxicity or rapid changes in seizure frequency. In addition, we recommend that a haematology and biochemistry test is performed every two weeks, three months, six months, and then every year. We may consider another drug as an ‘add-on’ if the phenobarbital level is reasonable but seizures are still frequent.
Phenobarbital can cause dogs to be ataxic (wobbly), eat more, drink more, urinate more, and gain weight. Rarely, it can cause skin lesions, liver damage, and bone marrow dysfunction. It is recommended to have regular blood tests to monitor for possible liver damage and bone marrow toxicity. We would also suggest checking a phenobarbital level in the event of clinical signs related to toxicity; or rapid changes in the frequency of seizure. If there is concern about the liver’s function, we often suggest running a pre- and post-prandial bile acid test.
Tell me more about Potassium Bromide (KBr)
Halide salts like KBr are used to treat epilepsy and are marketed under the names “Libromide” and “Epilease”. The drug is approved for use as an ‘add-on’ therapy in dogs. It is recommended to start with 30 mg/kg given once daily (either in one dose or divided into two doses given in the morning and evening). To check that KBr serum concentrations are at effective levels, we recommend reviewing them every 3 months, after 6 months, and then every 12 months thereafter. The side effects usually last for three weeks and are transient. These include drinking more, urinating more, wanting to eat more and wobbliness (behavioural changes in rare cases). Vomiting and diarrhoea are common gastro-intestinal side effects. Problems with the skin are uncommon. It will take 3 months for this drug to take effect.
You should not feed a pet salty food (e.g. crisps) or allow them to drink salty water as this will dramatically change their drug levels. Potassium bromide, however, should not be given to cats due to the high risk of potentially life-threatening side effects.
Tell me more about Imepitoin
In a similar way to other AEDs, imepitoin (tradename ‘Pexion’) suppresses seizure activity.
The recommended dose is 10-30 mg/kg twice a day. In order to control seizures, the starting dose is usually 10mg/kg twice daily, for instance, a 30kg Golden Retriever will get 300mg twice daily. The dose may gradually be increased up to the maximum recommended dose based on how well the seizures are controlled, usually over a few weeks.
There are fewer side effects with this drug compared to some of the other AEDs (including phenobarbital). Among them are increased drinking, urinating, eating, ataxia (wobbliness), restlessness, and sedation. It is also possible for them to cause side effects in the gut. It is not necessary to perform blood tests to check on this drug. Generally, this drug is more effective in dogs with few seizures, and is not often prescribed on its own in cases of multiple seizures or progressive epilepsy.
Tell me more about Levetiracetam
The human medication levetiracetam (Keppra) is not licensed for use in dogs, but we have a lot of experience with its use. The drug works very quickly, but it may only be effective for 2-4 hours if used for a short period of time. Patients with liver disease can also benefit from its safety. The drug’s effects may diminish with time if used on a long-term basis, so we usually use it only in an emergency to prevent seizures. Drowsiness and wobbliness are possible side effects, and they may be worse in patients taking other medications.
What are the options if the pet is not responding to AEDs?
Treatment may not work for an animal for many reasons:
- A mistaken diagnosis of idiopathic epilepsy (i.e. if there is an identifiable underlying cause),
- Antiepileptic drugs chosen inappropriately (such as diazepam for dogs),
- An insufficient dosage of medication has been administered.
- The development of ‘resistance’ to the effects of the drug (also known as drug-resistant epilepsy or refractory epilepsy).
A drug-resistant epileptic animal is one that suffers frequent and/or severe seizures despite receiving an appropriate dose and choice of medication.
A first line of treatment for refractory epilepsy in dogs is to add bromide to phenobarbital. For some dogs, an initial high dose of bromide (five times the usual daily dose for five days) may be required to quickly reach effective blood levels. It is possible to add human anti-epileptic drugs to the treatment, such as levetiracetam (Keppra), if the dog is already receiving phenobarbital and bromide. In dogs who tend to have severe cluster seizures, diazepam can be administered as a suppository or rectal solution at home. The goal is to reduce the number of seizures per cluster.
Does a dog need to stay on anti-epileptic drugs for life?
The majority of pets require lifelong treatment for this condition. The pet’s treatment should not be changed or stopped without veterinary advice. A pet should only be considered for dosage reduction if they haven’t experienced any seizures in the past year. Changing anti-epileptic drug levels suddenly can cause seizures. Reducing drug doses should be done very gradually over a long period of time. If the pet is not experiencing major side effects, there should be no concern about continuing treatment.