Don't do anything like that unless you know something about how to undo it.
Urging caution sounds wise, but I think it's exactly wrong here. One's goal in giving advice should be to alter others' behavior in beneficial ways; people will probably tend to take fewer risks with emetics than is optimal (because they're risk-averse, and vomiting is unpleasant), so your advice is in the wrong direction. Caution (higher significance criterion) is the act of increasing missed opportunities (false negatives) so that you take less wrong actions (false positives); this is a tradeoff.
This is analogous to how, for instance, the FDA kills more people by delaying medications' approval than it saves by ensuring medication is safe before approving it.
All over this thread, people keep urging caution where my judgment is that they should be urging the exact opposite.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.