However, the researchers stress that they haven't shown that either compound is safe or effective in treating Parkinson's disease.
"This study was not designed to determine if either agent is actually effective in slowing the clinical progression of Parkinson's disease," write Bernard Ravina, MD, and colleagues.
"Therefore, neither creatine nor minocycline should be used clinically for treating Parkinson's disease based on the results of this study," Ravina's team continues.
The study appears in Neurology's advance online edition.
About the Compounds
Here's how the study describes the two compounds:
- Creatine is a dietary supplement that has generally been used to improve athletic performance.
- Minocycline is an antibiotic that's been used to treat conditions including acne and rheumatoid arthritis.
Ravina and colleagues studied 200 people with early Parkinson's disease. Participants had had Parkinson's for up to five years and didn't yet require medicine to manage their symptoms.
Parkinson's disease affects certain brain cells. Those cells make dopamine, a chemical that helps direct movement. As those cells falter and die, dopamine levels drop, leading to problems including tremors, body stiffness, poor coordination, and slow movement.
Current Parkinson's treatments can help manage symptoms to some extent but may become less effective as the disease progresses.
Drugs 'Not Futile'
Every day for a year, participants took either creatine, minocycline, or a drug containing no medicine (placebo). They didn't know which treatment they had been given.
Both creatine and minocycline were "not futile" in slowing Parkinson's progression, the researchers write. "Not futile" means that the compounds didn't appear to be worthless, but it doesn't prove it met standards for effectiveness.
Creatine and minocycline might be candidates for further research, write Ravina and colleagues. However, they note that considerations such as safety, tolerability, activity, cost, and availability must first be weighed.
Both compounds were generally well tolerated, but minocycline was "less well tolerated" than creatine, the researchers write.
'Encouraging' Early Results
The National Institutes of Health (NIH) and National Institute of Neurological Disorders and Stroke (NINDS) organized the study as part of a larger project on Parkinson's disease. A long list of doctors from across the U.S. are working on the project.
"We are encouraged not only by these preliminary results, but also by the level of collaboration in the Parkinson's community," NINDS Director Story Landis, PhD, says in a NIH/NINDS news release.