Check out [Gerald Maguire's work](https://scholar.google.com/scholar?hl=en&as_sdt=0%2C22&q=gerald+maguire+stuttering&btnG=&oq=gerald+m) if you're curious about pharmacological research on stuttering. I saw him speak at an academic conference and he's very honest and straightforward about the research process, treatment results, side effects, etc.