Can a Parkinson’s Drug Treat Macular Degeneration?
By Serena McNiff
WEDNESDAY September 16, 2020 (HealthDay News) – A drug long used to treat Parkinson’s disease may benefit patients with severe age-related macular degeneration (AMD), a small clinical trial suggests.
One of the main causes of vision loss in older people is a condition called dry macular degeneration. More than 15% of Americans over 70 have AMD, and 10% to 15% of these cases develop more severe wet macular degeneration, which can lead to rapid and complete vision loss.
Usually, wet AMD is treated with drug injections into the eye. Most people need it every year to keep the disease from progressing.
But this small, early-stage clinical trial suggests that an alternative may be on the horizon: the main drug used to treat Parkinson’s disease, called levodopa.
The trial was the result of a 2016 study that found that patients with Parkinson’s disease who took levodopa were less likely to develop macular degeneration.
“The study found a relationship between taking levodopa and macular regeneration,” said Dr. Robert Snyder, professor of ophthalmology at the University of Arizona, Tucson. “It delayed the onset of wet and dry macular degeneration, and reduced the chances of wet macular degeneration.”
Macular degeneration affects the macula, the part of the eye that allows you to see fine detail. Wet AMD occurs when abnormal blood vessels develop under the macula; often these blood vessels leak blood and fluids, causing rapid damage.
Snyder and two colleagues began a clinical trial in 2017 to find out whether levodopa could help prevent both forms of AMD.
Twenty patients newly diagnosed with AMD participated in the first trial. Each received a small daily dose of levodopa for a month.
An ophthalmologist assessed them weekly to determine if they also needed an eye injection. Since the trial was based on preliminary research, the authors wanted patients to be given injections if needed, to make sure their condition wouldn’t worsen if levodopa was ineffective.
“Instead of injecting them, which would have been the standard of care, we treated them with levodopa and monitored them weekly to make sure they didn’t get worse,” Snyder said. “And if they got worse, we sent them back for an injection.”
After one month, all participants joined 11 new enrollments in a second trial to assess the safety and effectiveness of levodopa at different doses.
Although many participants required an injection during the trial, they required fewer shots than what would normally be given over a period of one month. Taking levodopa also appeared to delay the need for an injection, according to the study.
The authors reported that taking levodopa improved participants’ overall vision. It also greatly reduced the buildup of fluid in the eye.
The drug has been shown to be safe and well tolerated, the researchers said. Patients who experienced side effects associated with the drug, such as nausea and blurred vision, received a lower dose.
But this type of “open trial” has certain limitations. There was no point of comparison, like a placebo; all participants received levodopa. And the researchers and participants all knew what treatment was being given, which could lead to bias in the results.
Dr Raj Maturi, clinical spokesperson for the American Academy of Ophthalmology, said confirming the drug’s safety and effectiveness will require a larger and more robust clinical trial.
Maturi also expressed concern about the potential side effects of levodopa, especially given the age of the population affected by macular degeneration.
“You talk about a population of 70 and 80 years old – they already have other things to do,” said Maturi. “Any additional oral systemic medication that they will take for the rest of their life can dramatically affect their quality of life. I am always concerned about the side effect profiles of oral medications that need to be taken for a long time.”
While the second part of the trial is underway, the first results were published online recently in The American Journal of Medicine. Snyder said a larger study is coming.
“We were convinced that we had had a positive effect and that we had proof of concept to go ahead with a larger, placebo-controlled clinical trial,” he said. “This will be our next step.”
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