The NINDS NET-PD investigators will test creatine, a nutritional supplement, to determine if it slows the clinical decline seen in patients with PD.

In this study, 1720 men and women with early, treated PD will receive the investigational drug creatine or a matching placebo (an inactive substance). Each participant will have a 50 percent chance of receiving the creatine or placebo.

Creatine is a widely used dietary supplement thought to improve exercise performance. Creatine has not been approved to treat PD or any other neurological disorder.

In animal models, creatine has been shown to protect brain cells, and this agent is well tolerated in short human studies.

Although basic forms of the supplement are generally available on retail shelves, the creatine used in this study is significantly different. It is a clinical form, called PD-02, and is provided to the study investigators by Avicena Group, Inc.

Some of the known side effects of creatine are weight gain, swelling in the arms or legs, nausea, vomiting, and diarrhea. Side effects that are rare include muscle cramps, and liver or kidney problems.