Heart Medicine (未来の薬) is an antiviral drug that was created by Future Bulma in Future Trunks' alternate timeline. It is capable of curing the deadly heart virus that Goku contracts 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 episode, when Yamcha gives Goku the medicine it appears to be in a yellowish color. In following episodes, it is teal instead.
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 recover 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 medicine itself takes time to take effect. As such, if the victim has been in a high stage of infection, they will experience excruciating chest pains for quite some time. Once the medicine begins to take its toll on the virus, the victim will rest easier, having chest pains on and off until the medicine successfully destroys the virus.
The Heart Medicine appears as an item in the Budokai series, where it is a single slot technique called Vaccine which nullifies Viral Heart Disease's effect: 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.
In Dragon Ball Z: Sagas, the Antidote for Goku must be found in the city in one of the missions in Future Trunks' timeline.