Double-blind carbidopa/levodopa and placebo study in tardive dyskinesia.

The receptor sensitivity modification theory proposed as a potential treatment for tardive dyskinesia states that dopamine sensitivity can be down-regulated by temporarily increasing dopamine levels. We present a preliminary report of a double-blind carbidopa/levodopa-placebo study based on this hypothesis. Fifteen patients completed this 20-week trial. Based on the total tardive dyskinesia scores (using the Abnormal Involuntary Movement Scale) in the beginning and end of the study, patients were grouped as improved, same or worse. The six placebo-treated patients were equally represented in all three groups, but the distribution in the carbidopa/levodopa group was bimodal: five improved, four worsened, and none remained the same. This observation lends some support to the above theory.