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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 Status Epilepticus

15 to 20 mg PE/kg IV at 100 to 150 mg PE/min followed by maintenance doses of either fosphenytoin or phenytoin

Comments:
-The dose, concentration, and infusion rate of this drug should always be expressed as phenytoin sodium equivalents (PE).
-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.

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

Usual Adult Dose for Epilepsy

-Loading dose: 10 to 20 mg PE/kg IV or IM as a single dose
-Maintenance dose: Initially 4 to 6 mg PE/kg/day in divided doses at a rate no greater than 150 mg PE/min (maintenance doses should be started at the next identified dosing interval after administration of the loading dose); after the initial maintenance dose, subsequent doses should be individualized by monitoring serum phenytoin concentrations

Comments:
-The dose, concentration, and infusion rate of this drug should always be expressed as phenytoin sodium equivalents (PE).
-When treatment with oral phenytoin is not possible, this drug can be substituted for oral phenytoin at the same total daily phenytoin sodium equivalents (PE) dose.
-Because of the risks of cardiac and local toxicity associated with IV administration, oral phenytoin should be used whenever possible.
-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

Usual Pediatric Dose for Status Epilepticus

Less than 17 years:
15 to 20 mg PE/kg IV at a rate of 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower) followed by maintenance doses of either fosphenytoin or phenytoin

Comments:
-The dose, concentration, and infusion rate of this drug should always be expressed as phenytoin sodium equivalents (PE).
-IM administration of this drug should ordinarily not be used in pediatric patients. When IV access is impossible, loading doses can be given by the IM route.
-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.

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

Usual Pediatric Dose for Epilepsy

-Loading dose: 10 to 15 mg PE/kg IV at a rate of 1 to 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower)
-Maintenance dose: 2 to 4 mg PE/kg given 12 hours after the loading dose and continued every 12 hours (4 to 8 mg PE/kg/day in divided doses) at a rate of 1 to 2 mg PE/kg/min (or 100 mg PE/min, whichever is slower)

Comments:
-The dose, concentration, and infusion rate of this drug should always be expressed as phenytoin sodium equivalents (PE).
-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.

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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