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(fosphenytoin sodium) Injection
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.
The chemical name of fosphenytoin is 5,5-diphenyl-3-[(phosphonooxy)methyl]-2,4-imidazolidinedione disodium salt. The molecular structure of fosphenytoin is:
The molecular weight of fosphenytoin is 406.24.
IMPORTANT NOTE: Throughout all CEREBYX® product labeling, the amount and concentration of fosphenytoin are always expressed in terms of phenytoin sodium equivalents (PE). Fosphenytoin's weight is expressed as phenytoin sodium equivalents to avoid the need to perform molecular weight-based adjustments when substituting fosphenytoin for phenytoin or vice versa.
Care should be taken to ensure that CEREBYX is always prescribed and dispensed in phenytoin sodium equivalent (PE) (see DOSAGE AND ADMINISTRATION).
What are the possible side effects of fosphenytoin (Cerebyx)?
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Tell your caregivers at once if you have a serious side effect such as:
- severe burning, itching, swelling, redness, or skin discoloration anywhere in the body;
- problems with vision or speech;
- feeling like you might pass out;
- chest pain, irregular heart rhythm, feeling short of breath;
- fever, swollen glands, body aches, flu symptoms;
- skin rash, easy bruising or bleeding,...
Last reviewed on RxList: 3/16/2016
This monograph has been modified to include the generic and brand name in many instances.
Additional Cerebyx Information
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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