Yeah there has been. Methylphenidate has the most research done on its impact to promote fluency. Here's a study of a randomized clinical trial using methylphenidate for individuals who stutter: [https://journals.sagepub.com/doi/10.1177/1060028015596415](https://journals.sagepub.com/doi/10.1177/1060028015596415) I've read some case reports on other ADHD medications exacerbating or even improving stuttering in some, even methylphenidate has some case reports of it inducing stuttering. Research is quite mixed in this area, but one thing is emerging in the literature, which is there's a relationship between ADHD and stuttering. I think this is quite interesting.