Dose-response relationship of levodopa with mood and anxiety in fluctuating Parkinson's disease: A double-blind, placebo-controlled study

We investigated the effect of levodopa on mood and anxiety in eight Parkinson's disease patients with motor fluctuations. Each patient received 0.0-, 0.5-, and 1.0-mg/kg/hr levodopa infusions in randomly assigned order under double-blind conditions on consecutive days. Mood elevation and Anxiety reduction based on half-hourly patient rating and a corresponding increase in tapping speed occurred with active drug infusion but not placebo infusion. The effects were dose related. The higher-dose infusion rate produced more rapid onset, greater magnitude, and longer duration of response. We conclude that mood and anxiety fluctuations related to levodopa dosing are robust pharmacologic, and not placebo, effects.