Researchers are planning a phase I clinical trial to test the dyskinesia-relieving effects of ketamine.
Parkinson’s disease, a motor system disorder, is characterized by tremor, limb stiffness, impaired balance, and slowness of movement, as well as impaired movement coordination.
There is currently no known cure for this disorder, so treatments focus largely on managing the symptoms.
This helps people maintain autonomy and quality of life, as much as possible.
One of the main drugs used to treat Parkinson’s disease is levodopa, which can help with limb stiffness and slowness of movement. But there is a caveat: patients for whom levodopa does work begin to experience potentially debilitating side effects after a few years on the drug.
“The problem is levodopa works great for a few years — we call that the ‘honeymoon’ period — but then you start getting these side effects,” notes Dr. Scott Sherman, a neurologist at the University of Arizona College of Medicine in Tucson.
So what happens to many patients who take levodopa? They develop dyskinesia, or involuntary and uncontrollable movements that can affect the limbs, the head, or even the entire body, to various degrees of severity.
Once an individual develops levodopa-related dyskinesia, it does not go away unless treatment with this drug is discontinued altogether — though this may mean that their symptoms will no longer be managed.
But is there anything that could counteract levodopa’s side effects? Dr. Sherman and colleague Torsten Falk believe that the answer may lie with ketamine.
Ketamine’s effect on dyskinesia
Dr. Sherman and Falk found the first clues about ketamine’s potential in offsetting dyskinesia when they tested it as a pain-relieving drug for patients with Parkinson’s.
Their trial led them to observe an unintended yet welcome effect: dyskinesia was ameliorated, or even disappeared completely for a few weeks in the case of individuals on levodopa who were also administered ketamine.
When the researchers tried to duplicate these findings in a rat model, they found that the dyskinesia-offsetting effects of ketamine held strong.