Long-duration response to levodopa.

We measured the long-duration response to levodopa by changes in tapping rate in 16 patients with Parkinson's disease undergoing 3 to 5 days of levodopa withdrawal. "Off" tapping rates deteriorated 22% over the course of this holiday, the decline beginning 24 hours after levodopa withdrawal. Deterioration was more pronounced in the more affected hand in asymmetrically affected patients. A 2-hour infusion of levodopa after the levodopa holiday did not restore the long-duration response, although it produced a greater short-duration response than before the holiday. These observations indicate that the long-duration response is an important component of the therapeutic benefit of levodopa and is separable from the short-duration response.