Low Dose Apomorphine and Parkinsonism

The goal of the study is to learn why some people with Parkinson's disease (PD) get worse right after taking PD medication such as carbidopa/levodopa or as the medication is wearing off. In this study scientists will determine if apomorphine, a drug used to treat symptoms of PD, will worsen the motor symptoms of people with PD when low doses of the drug are given as a continuous subcutaneous infusion. A continuous subcutaneous infusion means the drug is administered continuously through a small needle placed under the skin. Apomorphine, a PD drug that works similar to carbidopa/levodopa, will be used in this study because it is faster-acting and has a more brief effect than carbidopa/levodopa. After the initial screening, participants will enter a 3-day treatment phase during which they will receive in random order low dose apomorphine, high dose apomorphine, or placebo (inactive substance). All participants will receive the study drug for 2 of the days at 2 different doses (low and high) and a placebo for 1 day. During the 3 days participants will provide blood samples and have their hearts monitored. Parkinsonism will be monitored each day by speed of finger tapping, foot tapping and walking as well as tremor and dyskinesia scores. Duration of the study for participants is approximately 4 to 5 days including 1-2 outpatient visits and a 3-day inpatient hospital stay.