Cerebyx (Fosphenytoin)

Cerebyx (fosphenytoin) is an injectable medication marketed by Pfizer and approved by the U.S. Food and Drug Administration (FDA) to help control generalized tonic-clonic status epilepticus seizures and for the prevention and treatment of seizures occurring during brain surgery.

Cerebyx can be used from birth without age limitation.

How Cerebyx works

Neurons or brain cells communicate with each other via electric signals. Sodium channels that are found on the surface of neurons are involved in signal transmission. Batten disease patients experience different types of seizures, including status epilepticus, in which the neurons send electrical signals uncontrollably.

Cerebyx acts on sodium channels keeping them open, which prolongs the inactive state of the neurons for longer after activation. This reduces the uncontrolled firing of neurons that causes seizures.

Cerebyx in clinical trials

An ongoing Phase 3 clinical trial (NCT01870024) aims to compare the effectiveness of Cerebyx in combination with Klonopin (clonazepam), and Klonopin plus Ativan (lorazepam) in stopping generalized status epilepticus. The trial is currently recruiting patients at the Hôpital Lariboisière in Paris.

Another Phase 3 clinical trial (NCT01960075) aims to compare the effectiveness of Cerebyx, Keppra (levetiracetam), and valproic acid in stopping status epilepticus that is refractory to benzodiazepine treatment. The study is recruiting patients at 65 locations across the U.S.

Additional information

The anti-epileptic effect of Cerebyx is not immediate so it usually is used in combination with other anticonvulsants to stop seizures. Clinicians commonly use Cerebyx when status epilepticus cannot be controlled with benzodiazepines.

Cerebyx comes as an injectable formulation and it can be used short-term as an alternative to phenytoin taken by mouth when this kind of administration is not possible. Phenytoin is an anticonvulsant that is taken daily to reduce the frequency of seizures. The active ingredient of Cerebyx, fosphenytoin, is a prodrug of phenytoin, which is converted to phenytoin once inside the body. Phenytoin also is available as an injectable formulation, but Cerebyx is preferred because it is water soluble and can be infused more rapidly.

Rapid administration of Cerebyx is associated with an increased risk of adverse cardiovascular reactions. To avoid confusion, the dose is expressed as phenytoin sodium equivalents (PEs). The maximum dosing rate is 150 mg PE per minute for adults, and 2 mg PE per kilogram of body weight per minute (or 150 mg PE per minute, whichever is slower) for children.


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