[Pessimist]

Am I the only one bothered by using drugs for other puposes just because they noticed they seemed to work?

What does that say about their understanding of the mechanism by which the drug works?

[allmendream]

Well often times you do know the molecular target of the drug, but are unsure of the exact effects once the molecular target gets hit.

Biology is much more complex than “if A then B which derives C”. More like “A hits B that causes effects C,D,E,F,G and H. C and D are what we wanted, but it didn't do ENOUGH of it. E was unexpected, but everyone liked it, did we discover a drug for E? F G and H are side effects that nobody likes, can we reduce them?”

The mechanism for all this is most likely known, in that drug A hits bio-molecule B, and activated B does a lot of things, SOME of which we want, some of which we do not want, and other things we sometimes didn't expect.

Biology doesn’t have the easy answers.