The recent article by Dr Stanley Fahn1 well describes the importance of a controlled clinical trial to determine the effect of levodopa on Parkinson disease (PD). The frequency of adverse motor events ("wearing-off," "on-off," and dyskinesias) is not well established. Fahn states that after 5 years of levodopa treatment, 75% of patients no longer have a smooth, stable, and effective response.1 However, his estimate is based on a sample that included many patients who had used levodopa for more than 5 years (10-15 years, 37% of patients; >15 years, 8% of patients).2
Hutton JT, Tolosa ES, Capildeo R, Morris JL. Levodopa-Treated Parkinson Disease Has Better Long-term Outcome Than Previously Predicted. Arch Neurol. 2000;57(5):758–759. doi:
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