There are no hard and fast rules about when treatment should begin. Once anticonvulsant therapy has started it is likely that it will need to be continued life-long. However, there is evidence that better long-term control of epilepsy is achieved following early treatment. The big question is therefore when to start treatment?
• Multiple seizures are observed in a short period of time.
• Seizures occur more than once a month and /or the owner finds the frequency distressing.
• The seizures are becoming more frequent or more severe.
• An underlying progressive disorder has been identified as the cause of the seizures.
• Post-ictal signs are objectionable (eg aggression).
Image: Treatment should be started if an underlying progressive disorder has been identified as the cause of the seizures. In this dog the adversive posture was associated with a forebrain lesion - courtesy of Laurent Garosi, Davies Veterinary Specialists.
The ideal anticonvulsant drug can be given once daily, is cheap and has few side-effects. A wide range of drugs are available for the control of human epilepsy but few of these are effective in dogs due to altered pharmacokinetics. The most commonly used anticonvulsants in dogs are: phenobarbital and bromide.
Primidone is not recommended for the treatment of seizures in dogs or cats for a number of reasons:
1) it is rapidly metabolised by the liver into phenobarbital and PEMA
2) it is phenobarbital that is responsible for more than 85% of primidone’s anticonvulsant effect
3) primidone is more expensive than phenobarbital
4) it is less well tolerated, particularly with regard to its potential hepatotoxicity
Dogs receiving primidone can be safely converted to phenobarbital treatment with no loss of anticonvulsant effect. It is generally safe to simply swap animals from primidone to phenobarbital (250 mg of primidone is approximately equivalent to 60 mg of phenobarbital). Alternatively conversion may be done gradually over 2-3 weeks.
If the patient has been seizure free for a year drug withdrawal may be considered. Before withdrawing the drug therapy weigh up the pros (potential reduction in side effects and cost) and cons (potential seizure recurrence). Drug doses must be tapered slowly and withdrawal should take around 6 – 12 months to complete.
Information and guides for owners
The following downloads should answer many of the most common questions asked by your client.
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