Setting limits on dopamine... ideas?

[Bio-Cellular Enigma]

Observing a friend recently (researching a certain stimulant substance), SWIM was struck by the necessity for some kind of solid beginning and end-point with any research involving substances that increase or inhibit the reuptake of dopamine.

The beginning is there by default, but what defines the end? Left entirely alone, the only automatic one SWIM is aware of is when the substance in question runs out. This is obviously not sufficient in most cases.

SWIM had a minor brainstorm on this, and suggests researchers always create a solid endpoint before researching any substance in this category. It should be just as solid as if the substance ran out and was gone, as self-control can become as much a liability as an asset where brain chemistry issues are concerned. There's a lot of room for imagination here. Defining a time or place would be a good start, but it has to go much further than that. Ingestion of a potent dopamine antagonist would immediately terminate research, but there are clearly risks involved with this.

Comments, input, ideas? Or is "will power" sufficient to research these substances with minimal risk involved?