Share on PinterestScientists have developed a weekly injectable treatment for Parkinson’s disease. Chalit Saphaphak/Stocksy
- Parkinson’s symptoms develop slowly, most commonly after the age of 50, and include tremor, slowness in movement, limb stiffness, problems with gait and balance, sleep disorders, and mental health issues.
- People with Parkinson’s disease have to take several tablets each day to help alleviate their symptoms.
- Now, a team of scientists in Australia has developed a weekly injectable treatment for Parkinson’s disease.
- If further research proves the injection’s safety and efficacy, the long-acting implant could be life changing for people living with Parkinson’s.
Parkinson’s disease is the second most common neurodegenerative condition after Alzheimer’s Disease. It affects almost 1.1 million people in the United States and more than 10 million worldwide. Of these, 96% are diagnosed after the age of 50.
The condition occurs when nerve cells in an area of the brain called the substantia nigra stop producing enough of the neurotransmitter dopamine. This leads to a range of symptoms, including:
- Tremor, or shaking, in hands, arms, legs, jaw, or head
- Muscle stiffness
- Slowness of movement
- Impaired balance and coordination.
The two main treatments for Parkinson’s disease are levodopa (L-dopa), which nerve cells use to make dopamine, and carbidopa, which increases the efficacy of levodopa and helps minimize its side effects. However, people need to take the medications several times a day, which many find difficult to do.
Now, scientists in Australia have developed a long-acting injectable treatment combining the two medications. Because the implant releases the drugs slowly over seven days, people with the condition would no longer have to take multiple tablets every day.
The study findings suggest that the injection could be “a promising system for the delivery of levodopa and carbidopa for Parkinson’s patients”.
Sneha Mantri, MD MS, Chief Medical Officer for the Parkinson’s Foundation, who was not involved in the study, agreed:
“If this medication is safe and effective in humans, it could be an alternative for people with [Parkinson’s] compared to multiple daily pills.”
The findings are published in the journal Drug Delivery and Translational Research.
An alternative to multiple daily pills
The injection contains a combination of levodopa (L-dopa) and carbidopa, two drugs used together to treat Parkinson’s disease.
L-dopa can cross the blood-brain barrier into the central nervous system, where it is converted to dopamine. People with Parkinson’s take L-dopa to control the physical symptoms associated with the lack of dopamine production.
Clinicians prescribe carbidopa in combination with L-dopa to increase its efficacy within the nervous system, and help combat gastrointestinal symptoms, which are a common side effect of L-dopa.
The two drugs are usually taken in the form of capsules, containing a combination of the drugs in carefully calculated proportions. To reduce the chance of gastrointestinal symptoms, they should be taken with meals. As fat and protein can decrease the absorption of L-dopa, people must avoid high fat or high protein meals when taking the tablets.
How was the injection developed, and how does it work?
The newly developed injection also administers a combination of L-dopa and carbidopa in the form of an in-situ implant.
For their implant, the researchers used two organic polymers and a solvent, in different ratios to achieve the correct rate of drug release. Once the correct ratio was determined, levodopa and carbidopa were added to create the implant.
They performed several in-vitro tests to determine the effect of pH (acid/alkali balance), how easy it was to inject the implant, how rapidly the implant degraded and the drugs were dispersed, and the effect of the implant on cells.
They then tested the mechanism ex vivo in leg muscle tissue from a pig.
The implant performed similarly in vitro and ex vivo, releasing the drugs slowly over several days.
After injection into muscle tissue, pores formed on the surface of the implant, through which the drugs diffused into the tissue. Up to 90% of the drug was released over 7 days, and the implant broke down completely within 2 weeks.
The formula that the researchers developed was easy to inject, so they suggest that this could be a:
“Promising drug delivery system for Parkinson’s patients, which will reduce the dosing frequency in the elderly patients to once-a-week injection.”
Potential problems with long-acting injections
Jamie Adams, MD, associate professor of Neurology at the University of Rochester Medical Center, who was not involved in the study, highlighted potential problems with the treatment:
“Given fluctuations in Parkinson’s symptoms, it may be difficult to determine appropriate dosing for an entire week, and patients may still require oral medications or other therapies. If the weekly injection is dosed too high, that could also be problematic.”
And Mantri also raised some issues that will need to be addressed:
“Every medication is different, and this type of gel has not been used for [Parkinson’s] treatment before. However, many injectable medications carry the risk of injection site reactions (for instance, rash, nodules) related to the delivery method itself.”
Promising early development needs further testing
This is an early stage of development of a new mechanism of drug delivery for people with Parkinson’s disease. But it has the potential to transform treatment for elderly people with Parkinson’s.
However, there are several further stages of testing that would need to be undertaken before the implant could be licensed, as Mantri told Medical News Today:
“This is a very preliminary study, looking at how the new treatment behaves in the lab. Further testing on animals and then humans will be necessary as it moves forward in drug development.”
“I would like to see the results of animal testing, as well as human testing, to ensure that this is both safe and effective,” she added.
Adams agreed:
“This treatment is still early, and there needs to be human studies, including randomized controlled trials, evaluating safety and efficacy.”
“A weekly injectable therapy for Parkinson’s disease could reduce the burden of frequent medication dosing and may improve quality of life.”
— Jamie Adams
