The Concoction of Vitality is a vampiric artifact.
This magical potion allows a vampire to become human again, but only for 24 hours. Thus, the vampire can go out in the daylight, eat, breathe and do all the other things a human can. However, the vampire is also just as vulnerable to harm as any other human, and all Disciplines are temporarily lost. It takes four to six hours for the potion to take full effect. While mortal, the character will age as if he had never died.
Players Guide to the Sabbat, p. 153-154