8-Bit is right, Mirikon - drugs are for game purposes essentially toxins (and/or vice-versa) for the way the game handles them. However, 8-Bit, Mirikon is also right, in that certain drugs/toxins have a minimum effect, which do not get resisted. Gamma-scop, for example - even if you resist all the muscle-paralysis, it's still going to act as a truth serum for that hour it's in your system.
And SnowDragon, you're meaning leal - aka laes-light. I don't recall 'Pixie' being an official street name for it, but I can see where that might come from.