Uh, we don’t really know how our drugs work (especially the older ones). We have a vague understanding of their mechanisms, but we really don’t know how they work. We don’t even have a clear idea of what the structures of most drugs look like, and how they interact with their binding sites.

Luckily, we don’t actually have to know how they work, to know that they work. Instead we use clinical trials and real world evidence to support their use.

(Fun fact: there’s actually a branch of drug development called phenotypic drug discovery which actually does away with the understanding of the mechanisms altogether. )