– Phenytoin (5,5-Diphenylhydantoin) is a hydantoin derivative and a non-sedative antiepileptic agent with anticonvulsant activity. It potentially acts by promoting sodium efflux from neurons in the motor cortex, reducing post-tetanic potentiation at synapses. This prevents cortical seizure foci from spreading to adjacent areas and stabilizes the threshold against hyperexcitability. Additionally, it appears to reduce muscle spindle sensitivity to stretch, causing muscle relaxation.