Effects of thioridazine dosage on the behavior of severely mentally retarded persons.

A double-blind, placebo-controlled trial of thioridazine (Mellaril) was conducted with severely retarded patients. Subjects were assessed on a relatively low standardized dose as well as on the individual dosage that had previously been determined clinically as most effective. Both active drug conditions caused a reduction in hyperactivity, bizarre behavior, and self-stimulation. The standardized dose, which was less than half the mean titrated level, resulted in an equivalent therapeutic response. The need for more attention to dosage levels in future investigations was emphasized.