WARNING: CARDIOVASCULAR RISK ASSOCIATED WITH RAPID INFUSION RATES
The rate of intravenous CEREBYX administration should not exceed 150 mg phenytoin sodium equivalents (PE) per minute because of the risk of severe hypotension and cardiac arrhythmias. Careful cardiac monitoring is needed during and after administering intravenous CEREBYX. Although the risk of cardiovascular toxicity increases with infusion rates above the recommended infusion rate, these events have also been reported at or below the recommended infusion rate. Reduction in rate of administration or discontinuation of dosing may be needed (see WARNINGS and DOSAGE AND ADMINISTRATION).
CEREBYX® (fosphenytoin sodium injection) is a prodrug intended for parenteral administration; its active metabolite is phenytoin. 1.5 mg of fosphenytoin sodium is equivalent to 1 mg phenytoin sodium, and is referred to as 1 mg phenytoin sodium equivalents (PE). The amount and concentration of fosphenytoin is always expressed in terms of mg PE .
CEREBYX is marketed in 2 mL vials containing a total of 100 mg PE and 10 mL vials containing a total of 500 mg PE. The concentration of each vial is 50 mg PE/mL. CEREBYX is supplied in vials as a ready-mixed solution in Water for Injection, USP, and Tromethamine, USP (TRIS), buffer adjusted to pH 8.6 to 9.0 with either Hydrochloric Acid, NF, or Sodium Hydroxide, NF. CEREBYX is a clear, colorless to pale yellow, sterile solution.
CEREBYX is indicated for the control of generalized tonic-clonic status epilepticus and prevention and treatment of seizures occurring during neurosurgery. CEREBYX can also be substituted, short-term, for oral phenytoin. CEREBYX should be used only when oral phenytoin administration is not possible. CEREBYX must not be given orally.
Published Studies Related to Cerebyx (Fosphenytoin)
Fosphenytoin for seizure prevention in childhood coma in Africa: a randomized
clinical trial. 
in children with acute coma... CONCLUSION: A single intramuscular injection of fosphenytoin (20 phenytoin
Bioavailability of intravenous fosphenytoin sodium in healthy Japanese
To compare and evaluate the bioavailability for intravenous fosphenytoin sodium
with that of intravenous phenytoin sodium in Japanese subjects... In conclusion, fosphenytoin
sodium is considered to be a useful substitute for phenytoin sodium with almost
no associated injection-site reactions.
Initial EEG predicts outcomes in a trial of levetiracetam vs. fosphenytoin for
seizure prevention. 
Continuous electroencephalography (cEEG) is increasingly used to detect both
clinical and subclinical seizures in patients with traumatic brain injury (TBI)
or subarachnoid hemorrhage (SAH). We assess whether EEG findings predict outcomes
in TBI/SAH patients enrolled in a levetiracetam (LEV) vs... While it has been
shown that LEV is associated with better outcome than fos-PHT when used as
seizure prophylaxis in brain injury, aside from severity of generalized slowing,
electrographic findings of focal slowing, epileptiform discharges, and seizures
were not themselves associated with outcomes in patients with TBI or SAH enrolled
in a randomized clinical trial.
Blood pressure changes after intravenous fosphenytoin and levetiracetam in patients with acute cerebral symptoms. [2009.12]
PURPOSE: To study the incidence and extent of the occasionally noted hypotension after intravenous (IV) infusions of fosphenytoin (FOS) and levetiracetam (LEV) in patients presenting with acute cerebral symptoms... CONCLUSIONS: IV infusion of FOS in subjects presenting with acute cerebral symptoms may cause significant decreases in their blood pressure. This was not seen in patients receiving IV LEV infusions. Since maintaining adequate cerebral perfusion pressure is a key point in the management of patients with acute cerebral symptoms, the results of this study may carry a clinical impact on the management of this subgroup of patients.
BACKGROUND: Fosphenytoin, phosphate ester pro-drug of phenytoin, was developed to overcome complications associated with parenteral phenytoin administration in treatment of acute symptomatic seizures, short-term prophylaxis and treatment of repetitive or prolonged seizures and status epilepticus. OBJECTIVE: To evaluate the current position of fosphenytoin in treatment algorithms compared to phenytoin... CONCLUSION: Published literature shows that intravenous fosphenytoin has a similar adverse effect profile than phenytoin when it is administered as recommended. There is no evidence of clear benefit that would justify the higher price of the fosphenytoin compared to phenytoin.
Clinical Trials Related to Cerebyx (Fosphenytoin)
Comparison Between Lorazepam, Clonazepam and Clonazepam + Fosphenytoin for the Treatment of Out-of-hospital Generalized Status Epilepticus [Recruiting]
The main purpose of this study is to know on one hand if lorazepam is more (effective) than
clonazepam and on the other hand if lorazepam is also effective as the association
clonazepam + fosphenytoin in out-of-hospital treatment of the generalized convulsive status
epilepticus in adult patients.
IV Keppra in the Emergency Department for Prevention of Early Recurrent Seizures [Completed]
This study is looking at three seizure medicines. Patients with seizures are usually
treated with phenytoin (Dilantin) or Fosphenytoin. These medicines can be given
intravenously (IV)or by mouth. Another seizure medicine, levetiracetam (Keppra) can now be
given this way also. This study will compare IV phenytoin (Dilantin) and IV fosphenytoin to
levetiracetam (Keppra) in patients who have had a recent seizure. Only patients with a
history of seizures can be involved. The patient must present to the emergency department
within 4 hours of a seizure. The purpose of this study is to compare these three drugs,
phenytoin (Dilantin), fosphenytoin, and levetiracetam (Keppra). The investigators are
looking to see if these drugs can prevent another seizure in the next 24 hours. We are also
looking for any possible side effects.
Established Status Epilepticus Treatment Trial [Not yet recruiting]
The primary objective is to determine the most effective and/or the least effective
treatment of benzodiazepine-refractory status epilepticus (SE) among patients older than 2
years. There are three active treatment arms being compared: fosphenytoin
(FOS),levetiracetam (LEV), and valproic acid (VPA).
The second objective is comparison of three drugs with respect to secondary outcomes.
The final objective is to ensure that the trial is informative for treatment of established
SE in children by describing the effectiveness, safety, and rate of adverse reactions of
these drugs in children.
The Study of NPC-06 - Investigation of Safety, Efficacy and Pharmacokinetics of Fosphenytoin [Completed]
The study is to evaluate safety, efficacy and pharmacokinetics of intravenously administered
fosphenytoin in patients with neurosurgery, head trauma, epilepsy or status epilepticus who
are requiring a loading dose of phenytoin.
Intravenous Lacosamide Compared With Fosphenytoin in the Treatment of Patients With Frequent Nonconvulsive Seizures [Active, not recruiting]
This a phase 2 study comparing the efficacy of intravenous (IV) lacosamide (LCM) with IV
fosphenytoin (fPHT) in controlling frequent nonconvulsive seizures (NCSs), the Adverse
Events profile of LCM compared with fPHT when used to treat frequent NCSs, and length of
stay in an intensive care unit for subjects treated with LCM versus subjects treated with
fPHT. The trial will include a preacute-treatment period, an acute-treatment period, a
postacute-treatment period, and a long-term follow-up period.
Page last updated: 2014-11-30