Levodopa and receptor sensitivity modification in tardive dyskinesia

Area of Science:

• Neuroscience
• Pharmacology
• Movement Disorders

Background:

• Tardive dyskinesia (TD) is characterized by involuntary hyperkinetic movements.
• It is hypothesized to result from dopamine (DA) receptor hypersensitivity due to long-term neuroleptic treatment.
• Receptor hypersensitivity modification using DA agonists is a proposed therapeutic strategy for TD.

Purpose of the Study:

• To investigate the efficacy of levodopa, a DA agonist, in treating tardive dyskinesia.
• To assess whether levodopa can modify dopamine receptor hypersensitivity in TD patients.

Main Methods:

• Thirteen patients with TD received levodopa plus benserazide for 4-8 weeks.
• Levodopa dosage ranged from 3.0–9.0 g/day.
• Treatment effects were evaluated through blind assessments of videotaped patient movements before, during, and after treatment.

Main Results:

• TD scores moderately increased during levodopa treatment.
• TD scores returned to baseline after drug discontinuation in patients on concurrent neuroleptic medication.
• In neuroleptic-free patients, TD scores decreased by 25% in three individuals, with complete resolution in one younger patient.
• Psychological side effects, including depression and increased psychosis, were observed at higher doses.

Conclusions:

• Levodopa treatment, aiming to modify receptor sensitivity, is not an effective therapeutic approach for tardive dyskinesia.
• Further research into specific patient variables and alternative DA agonists may be warranted.