Fosphenytoin Sodium API is the disodium phosphate ester prodrug of phenytoin. It is an antiepileptic pharmaceutical ingredient designed to provide a water-soluble form of phenytoin. Chemically, it is 5,5-diphenyl-3-[(phosphonooxy)methyl]-2,4-imidazolidinedione disodium salt, with molecular formula C₁₆H₁₃N₂Na₂O₆P and molecular weight 406.24 g/mol. Its CAS Registry Number is 92134-98-0.
Fosphenytoin Sodium is a phosphate prodrug of phenytoin and is rapidly converted to phenytoin after administration. It is highly water-soluble compared with phenytoin and is used in pharmaceutical formulations for the management of seizures.
| Property | Value |
|---|---|
| CAS Number | 92134-98-0 |
| Molecular Formula | C₁₆H₁₃N₂Na₂O₆P |
| Molecular Weight | 406.24 g/mol |
| Chemical Form | Disodium salt |
| Chemical Class | Hydantoin anticonvulsant / phosphate prodrug |
| Appearance | White to off-white powder |
The USP monograph defines Fosphenytoin Sodium as containing 98.0%–102.0%, calculated on the anhydrous basis.
| Parameter | Specification |
|---|---|
| Appearance | White to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.5% |
| Heavy Metals | NMT 10 ppm |
| pH (1% Solution) | 2.0 – 4.0 |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | 21.7% – 25.7% |