Recent important trials of pharmacotherapy in Parkinson's disease

Parkinson's disease (PD) affects approximately 1% of individuals > 60 years. Of these PD patients approximately 40% suffer dementia in later life. Levodopa is commonly used in the treatment of PD. Experimental evidence suggests that the dopamine synthesised from levodopa may contribute to the further degeneration of dopaminergic neurons. The results of the clinical outcome part of the Earlier Versus Later Levodopa Therapy in PD study suggest that levodopa slows the progression of PD. In contrast, the single photon emission-computed tomography imaging substudy was not conclusive but suggested that levodopa hastened the progression of PD. Thus, further studies of the effects of levodopa on the progression of PD are needed before it can be proved that levodopa does not have a detrimental effect on dopaminergic neurons. In a clinical trial of the anticholinesterase rivastigmine, a small improvement was observed in some patients suffering from dementia associated with PD. This small benefit has to be balanced against cholinergic side effects and a possible loss of efficacy of antimuscarinic agents used for motor control in PD.