Halacha is
In Memory of
Yona Ben Zeev , Pnina Bat Tzvi , Nehama bat schlomo ha cohen, Rajel Bat Yaacov, Tzvi ben DOV Beer ,
"On beloved memory o my parents and grandparents "
The Mishna establishes the Halacha "En Maftirin Ahar Hapesah Afikoman"-One may not eat after eating the Masa of the Afikoman. There is a disagreement between the Rishonim whether this prohibition includes drinking as well. Maran rules that it does include drinking. He allows only to drink water after the Afikoman.
There is a discussion as to the reason for this prohibition. Some suggest that it is to ensure that the taste of the Afikoman lingers in his mouth all night. Eating or drinking would dilute the taste.
Interestingly, the Rema brings down the Rambam's practice to drink a fifth cup of wine and recite on it the Hallel HaGadol. This is not the accepted practice. Drinking wine after the four cups is problematic, because it is likely to make a person drowsy and hinder him from fulfilling the Misva of staying awake as long as he can after the Seder, relating the wondrous miracles of the exodus. The custom is to also read Shir HaShirim after the songs of Nirsa.
SUMMARY One may not eat or drink anything except water after the Seder. One should stay awake as long as he can after the Seder to continue discussing the story of the exodus.