Phenytoin-d₁₀is intended for use as an internal standard for the quantification of phenytoin by GC- or LC-MS. Phenytoin is an anticonvulsant agent and active metabolite of fosphenytoin . Phenytoin is formed from fosphenytoin by tissue phosphatases.¹It inhibits neuronal voltage-gated sodium channels in a voltage-dependent manner.²Phenytoin reduces the neuronal firing frequency and decreases the amplitude of excitatory post-synaptic potentials (EPSPs) in electrically stimulated rat corticostriatal slices (EC₅₀s = 42.8 and 33.5 µM, respectively).³It protects against seizures induced by maximal electroshock (MES) in mice (ED₅₀= 10 mg/kg).⁴Formulations containing phenytoin have been used in the treatment of tonic-clonic seizures and status epilepticus.

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