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Fosphenytoin (Cerebyx ®)
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Standard Dilutions [Amount of drug] [Infusion volume] [Infusion rate]
| [100 to 1250 mg PE][50 ml] [10 min or greater]
Max rate: 150 mg PE / minute
Stability / Miscellaneous
Water soluble prodrug of phenytoin.
Fosphenytoin offers many advantages over phenytoin: minimum phlebitis, complete IM absorption, and the ability to administer the drug much more rapidly.
DOSAGE AND ADMINISTRATION
Products with particulate matter or discoloration should not be used. Prior to IV infusion, dilute Cerebyx in 5% dextrose or 0.9% saline solution for injection to a concentration ranging from 1.5 to 25 mg PE/mL.
2) Because of the risk of hypotension, fosphenytoin should be administered no faster than 150 mg PE/min. Continuous monitoring of the electrocardiogram, blood pressure, and respiratory function is essential and the patient should be observed throughout the period where maximal serum phenytoin concentrations occur, approximately 10 to 20 minutes after the end of Cerebyx infusions.
3) Because the full antiepileptic effect of phenytoin, whether given as Cerebyx or parenteral phenytoin, is not immediate, other measures, including concomitant administration of an IV benzodiazepine, will usually be necessary for the control of status epilepticus.
4) The loading dose should be followed by maintenance doses of Cerebyx, or phenytoin either orally or parenterally.
If administration of Cerebyx does not terminate seizures, the use of other anticonvulsants and other appropriate measures should be considered.
IM Cerebyx should not be used in the treatment of status epilepticus because therapeutic phenytoin concentrations may not be reached as quickly as with IV administration. If IV access is impossible, loading doses of Cerebyx have been given by the IM route for other indications.
Nonemergent Loading and Maintenance Dosing
The initial daily maintenance dose of Cerebyx is 4 – 6 mg PE/kg/day.
IM or IV Substitution For Oral Phenytoin Therapy
Dilantin capsules are approximately 90% bioavailable by the oral route. Phenytoin, supplied as Cerebyx, is 100% bioavailable by both the IM and IV routes. For this reason, plasma phenytoin concentrations may increase modestly when IM or IV Cerebyx is substituted for oral phenytoin sodium therapy.
The rate of administration for IV Cerebyx should be no greater than 150 mg PE/min.
In controlled trials, IM Cerebyx was administered as a single daily dose utilizing either 1 or 2 injection sites. Some patients may require more frequent dosing.
Dosing in Special Populations
2 mL per vial — Each vial contains fosphenytoin sodium 150 mg equivalent to 100 mg of phenytoin sodium:
Both sizes of vials contain Tromethamine, USP (TRIS), Hydrochloric Acid, NF, or Sodium Hydroxide, NF, and Water for Injection, USP.
Cerebyx should always be prescribed in phenytoin sodium equivalent units (PE) (see DOSAGE AND ADMINISTRATION above).
MADE IN IRELAND
Source: [package insert]