There have been studies with quite a few dopamine antagonists such as Olazapine and Risperdone. Nothing is FDA approved yet. Research has since moved on to different medications. From an OLD research article abstract "Olanzapine in the treatment of developmental stuttering: a double-blind, placebo-controlled trial" Apr-June 2004 *" Stuttering has been associated with excessive cerebral activity of the neurotransmitter, dopamine. Pharmacologic research has suggested that older generation dopamine antagonist (i.e. "typical antipsychotic") medications improve stuttering symptoms, but are associated with poorly tolerated adverse effects. "* [https://pubmed.ncbi.nlm.nih.gov/15328899/](https://pubmed.ncbi.nlm.nih.gov/15328899/)