I really don't know, but knowing PTerry's writing, the drugs might be harmless to a human, and a harmless troll drink might kill him, both being from a completely different set of the range of chemical substances... I don't remember from the top of my head wether there has ever been an indepth description of the troll body chemistry that would enable us to really clear that matter.

But seein Mr Tulip of all people snorts lots of slab in "The Truth", it has to be ineffective on the human body.
That was his trademark quirk after all - he was trying to have a drug habit, but failed miserably, snorting other things like flour, baking powder, curry etc.