CEREBYX®
(Fosphenytoin Sodium Injection)
DESCRIPTION
Cerebyx® (fosphenytoin sodium injection) is a prodrug intended for parenteral administration; its active metabolite is phenytoin. Each Cerebyx vial contains 75 mg/mL fosphenytoin sodium (hereafter referred to as fosphenytoin) equivalent to 50 mg/mL phenytoin sodium after administration. 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 is 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 converting between fosphenytoin and phenytoin sodium doses. Cerebyx should always be prescribed and dispensed in phenytoin sodium equivalent units (PE) (see DOSAGE AND ADMINISTRATION).
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