Psychosis
"My son had a severe acute psychosis and was put on haloperidol for about 2-3 days.  He had quite a bad reaction of dystonia (muscle stiffness) which is more common in young people and males (he was 17).  He had trouble swallowing, drooled, arched his back involuntarily, etc.  It was awful.  I do think it helped the psychosis somewhat, but he could not tolerate it."