Should dopamine agonists be given early or late in the treatment of Parkinson's disease?

The long term consequences of the use of a dopamine agonist, bromocriptine, in the treatment of Parkinson's disease are reported. In a first study in 82 patients showing late side effects of levodopa, bromocriptine permitted a significant decrease of the gastro-intestinal adverse effects. In contrast, no significant improvement of end of dose deterioration from levodopa was noted. In cases where levodopa had ceased to be active, bromocriptine produced an improvement in the clinical state. The drug was ineffective in the very advanced stages of the disease or in the cases of dyskinesias without "on-off" effects. Bromocriptine did not significantly improve freezing or "on-off" effects, but reduced other side effects of levodopa, in particular dystonia. In a second group of 29 patients who had never received levodopa treatment, bromocriptine was shown to be very effective as a first treatment of the disease. The most important finding was the absence of long term side effects similar to those usually observed under levodopa: in this group and in comparison with 38 patients taking levodopa, dyskinesia, dystonia, oscillations in performance and especially "on-off" effects were not noted. However, a partial loss of efficacy of bromocriptine was observed in 27% of cases. In a third group of 10 patients, bromocriptine introduced according to a low and slow protocol was found to be active in limited number of patients only.