This study will examine the effects of 24 weeks of lithium therapy achieving serum lithium levels of 0.25-0.50mmol/L on MRI and blood-based biomarkers in Parkinson's disease patients who have completed one of our current 24-week lithium clinical trials.

In observational studies, small daily doses of lithium from smoking cigarettes have been associated with a 77% reduced risk of developing Parkinson's disease (PD). In addition, lithium therapy has been effective in preventing neuronal death and behavioral symptoms in several PD animal models. Recently, our group has shown 24-weeks of low-dose lithium therapy in PD to be associated with improvements in both MRI and blood-based biomarkers implying that lithium may be slowing the progression of the disease. However, these findings stemmed from only three of four patients receiving MRIs. Our group is now conducting two larger studies enrolling a total of 35 PD patients who are being treated with either 45mg/day or 20mg/day of lithium or placebo therapy for 24 weeks. Because our earlier study showed maximum improvements in PD biomarkers in patients with serum lithium levels of 0.25-0.50mmol/L and there are large interpatient variations in serum lithium levels achieved from the same lithium dosage, this present study will adjust lithium dosing in each patient to achieve this target serum lithium level for an additional 24 weeks. MRI and blood-based biomarker changes from Baseline will be compared in patients with serum lithium levels ≥ 0.25mmol/L and <0.25mmol/L from one of the 24-week studies and within individual patients. Results from this study may identify a target serum lithium level range associated with maximum improvements in PD biomarkers that can be used in the design of future, larger lithium PD lithium trials, which may eventually support lithium as a disease-modifying therapy for PD that could improve patients' long-term prognoses.

1. All PD patients completing STUDY00007253 or STUDY00008239 at the University at Buffalo will be eligible.
2. No unstable cardiac, medical, neurologic or psychiatric condition in the opinion of the PI.
3. No current use of illicit drugs or current alcohol abuse in the opinion of the PI.
4. No history of brain surgery or possible need for brain surgery including deep brain stimulation (DBS) for at least 24 weeks in the opinion of the PI.
5. Women with child bearing potential will need a negative pregnancy test and not be nursing an infant at screening. Women with child bearing potential will need to report using barrier method or hormonal contraception.
6. Willing and able to sign informed consent and follow study procedures.

Patient demographics and outcome measure results.

IPD will be made available after the study results are published.

Researchers who have requested IPD from the PI.