The long duration response to levodopa in Parkinson's disease

The duration of effect of levodopa has been reported by some authors to be shorter in fluctuating parkinsonian patients with long standing disease than in stable patients. Other authors report no difference in the two groups of patients. We assessed motor fluctuations and response duration in 15 Parkinson's disease patients. Three patterns of response were observed: deterioration within one day on placebo and marked fluctuations on levodopa; deterioration after one day on placebo and moderate fluctuations on levodopa; no deterioration during 3 days of placebo and no fluctuations on levodopa. One patient who did not deteriorate or fluctuate did both when restudied 12 years later. This study confirms that, in addition to the short duration response to a single dose of levodopa, there is a long duration response to levodopa which is lost as the disease progresses. Loss of this long duration response to levodopa may be a key factor in the emergence of fluctuations in Parkinson's disease.