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Fosphenytoin Dosage

Applies to the following strength(s): 100 mgPE/2 mL ; 500 mgPE/10 mL

The information at Drugs.com is not a substitute for medical advice. Always consult your doctor or pharmacist.

Usual Adult Dose for:

Additional dosage information:

Usual Adult Dose for Status Epilepticus

-Loading dose: 15 to 20 mg of phenytoin sodium equivalents (PE)/kg IV at 100 to 150 mg PE/min
-Nonemergent maintenance dose: 4 to 6 mg PE/kg/day in divided doses

Comments:
-This drug should not ordinarily be given IM for the treatment of status epilepticus because therapeutic phenytoin concentrations may not be reached as quickly as with IV administration.
-Because the full antiepileptic effect of phenytoin is not immediate, other measures, including concomitant administration of an IV benzodiazepine, will usually be necessary for the control of status epilepticus.
-Because of the risk of hypotension, this drug should be administered no faster than 150 mg PE/min.
-Continuous monitoring of the electrocardiogram, blood pressure, and respiratory function is important and the patient should be observed throughout the period where maximal serum phenytoin concentrations occur, approximately 10 to 20 minutes after the end of the infusion.
-If this drug does not terminate seizures, the use of alternative anticonvulsants should be considered.
-The loading dose should be followed by maintenance doses of either fosphenytoin or phenytoin.

Use: For the control of generalized tonic-clonic status epilepticus

Usual Adult Dose for Epilepsy

-Loading dose: 10 to 20 mg of phenytoin sodium equivalents/kg IV or IM as a single dose
-Maintenance dose: 4 to 6 mg PE/kg/day IV or IM in divided doses
-IV or IM substitution for oral phenytoin therapy: This drug can be substituted for oral phenytoin at the same total daily dose. The rate of administration for IV should be no greater than 150 mg PE/min.

Comments:
-Because of the risks of cardiac and local toxicity associated with IV administration, oral phenytoin should be used whenever possible.
-Because of the risk of hypotension, this drug should be administered no faster than 150 mg PE/min.
-Continuous monitoring of the electrocardiogram, blood pressure, and respiratory function is important and the patient should be observed throughout the period where maximal serum phenytoin concentrations occur, approximately 10 to 20 minutes after the end of the infusion.

Use: Prevention and treatment of seizures occurring during neurosurgery and as a short term substitute for oral phenytoin

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Dose Adjustments

The dose is expressed as phenytoin sodium equivalents. Fosphenytoin may be substituted at the same total daily dose as phenytoin. Oral phenytoin may be used for maintenance therapy after the fosphenytoin loading dose.

Precautions

US BOXED WARNINGS:
Cardiovascular risk associated with rapid Infusion Rates:
-The rate of IV 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 IV administration of this drug.
-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.

Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.

Dialysis

Data not available

Other Comments

Storage requirements:
-The manufacturer product information should be consulted.

Reconstitution/preparation techniques:
-The manufacturer product information should be consulted.

General:
-This drug is not indicated and is not useful for the treatment of absence seizures.
-This drug can be substituted, short-term, for oral phenytoin, but only when oral phenytoin administration is not possible.
-This drug must not be given orally.
-Doses of this drug are expressed as their phenytoin sodium equivalents. Therefore, no adjustment is recommended when substituting fosphenytoin for phenytoin or phenytoin for fosphenytoin.
-This drug may be administered by IV or IM injection; however, the IM route should not be used for the emergency control of seizures such as status epilepticus.

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