Although patients with Parkinson's disease usually respond to dopaminergic therapy with a smooth, continued effect when medication is first initiated, many patients eventually develop a fluctuating response along with involuntary movements (dyskinesias). The fluctuations in motor response often result in patients requiring more frequent dosing of medication that is less convenient, and they begin to lose control of their daily life. Their ability to work or to perform activities of daily living may fluctuate with response to medication, and the involuntary movements may interfere with activities. The fluctuations and dyskinesias can be painful and quite embarrassing. Overall, quality of life suffers. In addition, there is a marked increase in the expense to both the patient and society when motor fluctuations and dyskinesias develop.