Which medications in the drug class Anticonvulsant Agents are used in the treatment of Status Epilepticus?

Updated: Feb 13, 2018
  • Author: Julie L Roth, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Answer

Anticonvulsant Agents

These agents are used to terminate clinical and electrical seizure activity and to prevent seizure recurrence. Since the full antiepileptic effect of phenytoin, whether given as fosphenytoin or parenteral phenytoin, is not immediate, use of these agents usually follows administration of an IV benzodiazepine.

Phenytoin (Dilantin, Phenytek)

Phenytoin blocks sodium channels in the CNS. It may act in the motor cortex, where it may inhibit spread of seizure activity. The activity of brainstem centers responsible for tonic phase of grand mal seizures also may be inhibited. The dose should be individualized.

A mainstay in the treatment of SE, phenytoin must be administered slowly and therefore takes longer than benzodiazepines to enter the brain. Phenytoin has the advantage of being a long-term anticonvulsant and can be administered orally after acute illness.

Phenytoin is not water soluble, and must be solubilized in propylene glycol carrier with pH 12 to prepare IV form; therefore, it cannot be given at a rate faster than 50 mg/min without risk of significant hypotension and cardiac arrhythmias, as well as major risk of potential irritation at IV site and vascular compromise of the infused limb. Therefore, its use in SE should be avoided if possible.

Fosphenytoin (Cerebyx)

A phosphorylated phenytoin prodrug, fosphenytoin is highly water-soluble at physiologic pH and therefore is easier to administer than phenytoin. It is hydrolyzed rapidly and completely to phenytoin by endogenous phosphatases after a mean of 8 min and therefore can be administered more rapidly than standard phenytoin. Fosphenytoin also eliminates the risk of phlebitis and purple-glove syndrome seen with phenytoin, while achieving therapeutic CNS levels as quickly as phenytoin.

To avoid the need to perform molecular weight–based adjustments when converting between fosphenytoin and phenytoin sodium doses, the fosphenytoin dose is expressed as phenytoin equivalents (PE).

IM administration of fosphenytoin has been approved. However IV is still the route of choice for SE. Cardiac monitoring is required when this agent is administered IV but is not required for IM administration.


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