From the Guidelines
For a female patient with recurrent seizures, noncompliance with Topamax, and an existing intravenous line, I would recommend administering intravenous phenytoin as seizure prophylaxis, given her allergy to Keppra. The most recent and highest quality study, 1, does not provide specific guidance on the choice of antiepileptic medication for seizure prophylaxis in this scenario. However, considering the patient's allergy to Keppra and the need for rapid seizure control, phenytoin is a suitable alternative. The loading dose should be 18-20 mg/kg IV at a rate not exceeding 50 mg/minute, administered as a piggyback infusion through the existing IV, as recommended in 1. This slow administration rate is crucial to prevent cardiovascular side effects like hypotension and arrhythmias. Key points to consider when administering phenytoin include:
- Continuous cardiac monitoring and frequent blood pressure checks during the infusion
- Maintenance dosing of 4-6 mg/kg/day divided into 2-3 doses after the loading dose
- Monitoring for side effects, including dizziness, nystagmus, and ataxia
- Checking blood levels after loading to ensure therapeutic range has been achieved. It is essential to note that while valproate may be considered as an alternative, its use is not recommended in this scenario due to the lack of specific guidance in the most recent study 1. Therefore, phenytoin remains the most appropriate choice for seizure prophylaxis in this patient, given its established efficacy and safety profile, as supported by 1 and 1.
From the Research
Seizure Prophylaxis Considerations
- The patient has a history of recurrent seizures and is noncompliant with Topamax (topiramate), which may increase the risk of seizures 2.
- The patient has an existing intravenous (IV) line, which could be used to administer IV seizure prophylaxis.
- The patient has an allergy to Keppra (levetiracetam), which limits the options for seizure prophylaxis.
Phenytoin as a Potential Option
- Phenytoin has been shown to be effective in reaching therapeutic levels in the cerebrospinal fluid (CSF) for seizure prophylaxis, especially when dosages approximate weight-based dosing 3.
- However, phenytoin has a narrow therapeutic window and requires therapeutic drug monitoring (TDM) to prevent adverse drug reactions (ADRs) such as ataxia, which has been reported in cases of phenytoin toxicity 4.
- Phenytoin has been recommended by the Brain Trauma Foundation and the American Academy of Neurology (AAN) for early post-traumatic seizure (PTS) prophylaxis 2.
Alternative Options
- Levetiracetam has been shown to be a reasonable alternative to phenytoin for seizure prophylaxis, especially in patients with an allergy to phenytoin or those who experience adverse effects from phenytoin 2, 5.
- However, levetiracetam may not reach therapeutic levels in the CSF as quickly as phenytoin, and its efficacy for seizure prophylaxis is still being studied 3, 5.
- Other antiepileptic drugs, such as valproate, lamotrigine, and topiramate, may also be considered for seizure prophylaxis, but their efficacy and safety profiles vary 6, 2.