II. Indications
- Status Epilepticus
- Seizure Disorder and unable to take oral medications
III. Contraindications
- Pregnancy
- Cardiac conduction delays
IV. Mechanism
V. Dosing
- Dosed in Phenytoin equivalents (PE)
- Transition to oral Phenytoin as soon as possible
- Therapeutic serum level range: 10 to 20 mcg/ml
-
Status Epilepticus
- Dose: 15 to 20 PE mg/kg IV or IM (at 3 mg/kg/min up to 100 to 150 mg/min) up to 1000 mg maximum
- Avoid IM dosing if possible
- Non-Emergent Loading Infusion
- Dose: 10 to 15 PE mg/kg IV (at 2 mg/kg/min up to 100 to 150 mg/min) up to 1000 mg maximum
- Maintenance
- Follows loading dose by 12 hours (Status Epilepticus or non-emergent loading)
- For initial dosing only (later dosing should be based on serum levels)
- Start: 2 to 4 PE mg/kg infused slowly (1-2 mg/kg/min up to 100 mg/min) every 12 hours
- Subsequent dosing (based on serum levels)
- Dose 4 to 8 mg PE/kg/day divided every 12 hours based on serum levels
- Preferred over Phenytoin for Status Epilepticus
- Fosphenytoin can be infused with dextrose
- Fosphenytoin has lower risk of Arrhythmia (due to no Ethylene Glycol in base)
- Fosphenytoin may be given IM or delivered a faster IV rate (not tissue toxic)
VII. Adverse Effects
- See Phenytoin
- Severe Hypotension and Cardiac Dysrhythmias
- Infuse slowly
- Cardiac and hemodynamic monitoring during infusion
VIII. Drug Interactions
- See Phenytoin
IX. Resources
X. References
- (2022) Presc Lett, Resource #361206, Antiseizure Medications
- Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 56-7
- Hamilton (2020) Tarascon Pocket Pharmacopoeia
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Definition (NCI) | A water-soluble phosphate ester prodrug of phenytoin, a hydantoin derivative with anticonvulsant activity. Fosphenytoin is hydrolyzed to phenytoin by phosphatases. Phenytoin exerts its effect mainly by promoting sodium efflux and stabilizes neuronal membranes in the motor cortex. This leads to a suppression of excessive neuronal firing and limits the spread of seizure activity. |
Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
MSH | C043114 |
SnomedCT | 108397000, 372484000 |
LNC | LP61620-8, MTHU021879 |
English | 2,4-Imidazolidinedione, 5,5-diphenyl-3-((phosphonooxy)methyl)-, (SP-4-2)-, 3-(hydroxymethyl)phenytoin phosphate ester, fosphenytoin, FOSPHENYTOIN, fosphenytoin (as phenytoin equivalent), fosphenytoin [Chemical/Ingredient], Fosphenytoin (product), Fosphenytoin (substance), Fosphenytoin |
Spanish | fosfenitoína (sustancia), fosfenitoína, fosfofenitoína (producto), fosfofenitoína (sustancia), fosfofenitoína |
Ontology: Cerebyx (C0525944)
Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
MSH | C043114 |
English | Cerebyx |