Levodopa in the treatment of Parkinson's disease: a consensus meeting.

Levodopa (in combination with a peripheral dopadecarboxylase inhibitor) substantially improves the quality of life of patients. However, physicians are not always comfortable prescribing it, and its administration is often delayed to retard the development of motor complications or is restricted to patients with relatively advanced disease, because there is a fear that the decreased response of parkinsonian symptoms may result from a self-limiting effect of the drug. Moreover, long-term treatment with levodopa is claimed by some to induce the degeneration of dopaminergic neurons, thereby accelerating disease progression. Whether long-term administration of levodopa in patients may result in the irreversible appearance of side effects or accelerate the neurodegenerative process is a crucial question, and it is therefore legitimate to ask whether one should delay the introduction or limit its use in patients. To address these questions, a meeting of experts was held in Paris (January 8–9, 1998) to see whether general agreement could be reached concerning the interpretation of studies of levodopa toxicity in tissue culture, in animal models of parkinsonism, and in patients. Most of the experts agreed that the administration of levodopa was not dangerous for patients. Nevertheless, there are still conflicting results and unanswered questions. This is why this consensus on levodopa treatment of patients with Parkinson’s disease (see below) is followed by additional comments made by some of the experts.