That was an experimental drug back in Japan in the 80’s - 90’s. Effects were thought to come from stabilising dopamine signalling in the basal ganglia–thalamo–cortical speech loop. It’s in the same conceptual category as: Tiapride Risperidone (low dose) Aripiprazole / Abilify (partial agonist rather than blocker) It’s essentially a dopamine modulator, very similar to what Abilify does. Some people here are using it off label for their stuttering, and have reported great success in improving fluency. To date, no medication is FDA approved specifically for treating stuttering, but other antipsychotic medications (listed above) are being used off-label for it.