At 14, I used to see a doctor who specialized in child and adolescent psychiatry (now I'm 25). Although he advised me to see a speech therapist (I and my family didn't know that there are such people in my country..), we still decided to try drugs to see how it goes. Among these drugs he prescribed, I remember some anti-psychotics and/or anti-depressants. At that time, they helped me a bit. The benefits were only temporary though. After I got fluent a bit for some time, the stuttering used to recur and get worse again. I guess such drugs are prescribed unofficially to treat stuttering probably because they have relaxing effects.