Heart Medicine (未来の薬, Mirai no Kusuri; lit. "Future Medicine") is the unnamed antiviral drug that was created in Future Trunks' alternate timeline. It is capable of curing the seemingly incurable and deadly heart virus that Goku and Future Goku contract during the Androids Saga.
At first, the medicine was seen as pills, but later on, it was seen as a liquid. When he first gets the Heart Medicine, Goku says the medicine's label is purple, leading him to believe it is grape-flavored (but this has never been confirmed). In a later episodes, when Yamcha gives Goku the medicine it appears to be in a yellowish color. In following episodes, it seems to be a teal liquid.
Once the virus is contracted, a steady supply of the heart medicine can cure the virus in only ten days for a normal Human (although Goku was able to cure much faster due to his Saiyan biology). As according to Future Trunks, it should take ten days for Goku to fully heal, but according to the timeline created in the Perfect Files, the entire time that Dr. Gero's creations were terrorizing the planet took place over the course of only a few days, and Goku was incapacitated for only a brief period of time in that entire time.
The Heart Medicine appears as an item in the Budokai series of video games where it is renamed "Vaccine". The "Viral Heart Disease" is a special technique item that causes both the user and opponent's health to deplete continuously, until only half of their last health bar is left. The user and opponent can avoid taking damage by equipping "Vaccine", a single slot technique which nullifies Viral Heart Disease's effect.