I'm sorry I can't find it either. Maybe it was a different podcast. I'm trying to think of other podcasts. I don't think it was RadioLab. Could have been another NPR show but I can't think which one would address this issue. HB seems like the best fit. I can bound the date of when I listened to it. Was definitely between 2018 and 2015. My intuition says 2017, because that was the height of my podcast listening. The time is probably why I can't remember in high detail.
Basically the story I remember is that there was a sports athlete that was in the lower ranks and then got a prescription, that they actually needed, that also improved their performance. Then I think it got banned? So they start buying it from another country like China or something. They then started buying in bulk because it was cheaper. Their friends started asking for some because he was getting it for cheap and he didn't think anything of it because he was just helping them save money too. They're his friends after all and he was already buying the stuff. So what difference did it make if he just ordered a little more? Then it started being friends of friends. Before he knew it he was selling tons of this stuff and to people he had no real previous knowledge of.
I now really want to listen to it again so if someone can help find it let me know. I think they might have also talked about Lance (I'm not sure if they interviewed him or that's another podcast I'm thinking of).