New directions in the drug treatment of Parkinson's disease.

Parkinson's disease, a clinical syndrome with 4 cardinal features (bradykinesia, resting tremor, increased muscular rigidity and impaired postural balance), is mainly caused by the loss of dopaminergic neurons in the substantia nigra pars compacta. Although levodopa remains the 'gold standard' in the treatment of the disease, several emerging strategies are currently being developed. The first concerns new symptomatic drugs that either potentiate the effects of levodopa (e.g. slow-release preparations of levodopa, catechol-O-methyltransferase inhibitors and new dopamine agonists) or target clinical symptoms resistant to dopaminergic drugs (e.g. glutamate antagonists). The second strategy is to find drugs that are able to prevent or delay the neuronal death observed in Parkinson's disease. Several neuroprotective drugs are now in development in experimental research, but clinical trials in this area are still lacking. The development of these new drugs also depends on the validation of new clinical methodologies.