The clinical relevance of levodopa toxicity in the treatment of Parkinson's disease

Levodopa is the 'gold standard' drug for the treatment of the motor symptoms of Parkinson's disease (PD). For many years there has been concern regarding its potential to be toxic to the dopaminergic cells of the substantia nigra. Much of the evidence to support this is derived from in vitro studies and there are significant limitations in extrapolating these data to the clinic. Indeed, there is no evidence to indicate that levodopa is toxic to PD patients, and even some suggestion that it may be protective.