white capsule pill with the number 402 ## Found a match it's Extended phenytoin sodium 100 mg, which is commonly used antiepileptic. Phenytoin acts to dampen the unwanted, runaway brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage gated sodium channels. To learn more click on the link below... Do you have any more questions or informaiton to add? Please post back if you do.