What is a cluster seizure?
Cluster seizures are defined as 2 or more discrete seizures within a 24 hour period. Cluster seizures are different than status epilepticus (any one seizure lasting for an extended period of time, or 2 seizures in which poor recovery occurred between seizures). Cluster seizures pose a special concern for seizure patients because of they have been linked with poorer outcomes compared to dogs without a history of cluster seizures.
The goal with cluster seizure management is to minimize the number and duration of seizures. A secondary goal is to reduce the need for hospital visit or stay thus reducing the financial burden to the client.
When should I provide a cluster seizure plan to a client?
If a patient has a history of 2 or more episodes of cluster seizures
If the patient has a history of status epilepticus
What drug choices, routes of administration and doses can I offer?
Levetiracetam
Rectal administration – 40 mg/kg per rectum (PR) at the time of seizure, repeated once if needed within 24 hours. Results suggest an improvement in seizure management in the medium term using rectal levetiracetam AND standard anticonvulsant therapy according to one study
Oral administration – start 20-30 mg/kg PO q8hr (NOT Extended release) levetiracetam after a pet experiences the first seizure and has recovered well enough to eat. Continue q8hr dosing for 2 days beyond the pet’s last seizure. The levetiracetam is then stopped, and the pet's long-term anticonvulsant therapy is continued. Clinical experience suggests this approach will reduce clinic visits, number of seizures during the cluster event. However, clinical side effects such as sedation or ataxia may be present during the dosing period. Note: This approach should NOT be used if levetiracetam is part of a patient’s standard oral therapy for long-term seizure control. Suddenly discontinuing an anticonvulsant medication can lead to breakthrough seizures or status epilepticus.
Benzodiazepine
Diazepam has been the main acute anticonvulsant treatment for veterinary patients.
Rectal - Be sure to target the rectum, not colon, to avoid hepatic metabolism. Start 1-2 mg/kg PR. Compounded suppository formulations of diazepam have not demonstrated reliable serum diazepam concentrations in dogs and therefore are not currently recommended.
Intranasal – preferred by some due to the ease of administration, and avoidance of the first pass effect of metabolism. Start with 0.5 mg/kg intranasal.
Midazolam
Intranasal – this is my preferred route and drug for at home benzodiazepine administration. Additionally, it was reported to be favorable compared to intravenous midazolam in 44 dogs.Start with 0.2 mg/kg intranasal.
Intramuscular – this route is favored by some but is not my recommended route of administration for clients at home in emergency situations. In a clinical situation, intramuscular administration can be effective when intravenous access is limited. Starting dose of 0.2 mg/kg is recommended.
Rectal – do not use midazolam rectally due to erratic and unpredictable plasma concentrations at standard doses.
Phenobarbital
Patients receiving daily phenobarbital administration can benefit from an increase, or pulse, of phenobarbital therapy during a cluster event.
Oral increase – in clinical practice we regularly recommend increasing a dog from q12h dosing to q8h dosing and continue this plan for 2 days beyond the last seizure. An example of this would be if a dog had a seizure Saturday morning. Upon recovery from the seizure an additional oral dose of phenobarbital (at the same oral dose administered) is recommended followed by q8hr dosing Sunday and Monday. Tuesday the dog would return to the standard twice daily dosing interval. This approach provides a slight increase of serum phenobarbital concentrations which may protect against further cluster seizures. Clinical adverse effects such as increased sedation, ataxia, polyuria, polydipsia, and polyphagia may become evident during the increased dosing period.
Summary
Providing options at home for cluster seizure care can reduce the need for hospitalization, and clinic visits. Additionally, any of the above treatments can be provided in hospital during seizure observation should that be needed. All the treatment choices discussed above are targeted for dogs and are rarely used in cats.
I hope your Tuesday isn't a cluster of craziness! As you well know, I enjoy helping you, help your patients with seizures live their best lives so please reach out if you're working through a case and need a little extra help. Have a great week!