This isn't a medicine but I used to take ecstasy a few times a week and that was when I had my best fluency. It was a long a time ago and my speech has gotten worse since I stopped. Not directly because of it (I think) but I did notice a huge difference when I was constantly taking it. Side note: I want to try micro dosing psilocybin mushrooms. I've read a lot about how it's really good at helping with anxiety and depression. My theory that I want to test on myself is that micro dosing might help with my stuttering. Personally, when I'm less depressed and anxious I notice a huge difference in my speech.