MILWAUKEE - A new skin patch to treat Parkinson's disease significantly improved symptoms, according to a study by researchers at the Medical College of Wisconsin and several other institutions.
By using a transdermal patch instead of conventional oral medication, doctors hope to get better control of Parkinson's symptoms while avoiding side effects. The study used a new drug, rotigotine, administered through an abdominal patch.
One problem with oral Parkinson's drugs is that levels of the drugs can vary substantially from hour to hour depending on how often the drugs are taken and how quickly they are cleared from the body.
By using a patch, patients can obtain a "steady state" of a drug, said the study's lead author, Karen Blindauer, an assistant professor of neurology and director of the movement disorders program at the Medical College of Wisconsin.
That's important because if drug levels are too high, it can cause involuntary twitching or jerking; and if levels are too low, symptoms can worsen, she said.
In addition, it is hoped that applying a patch once a day will help patients more closely comply with their medication regimen, Blindauer said.
"It's easier to take the [patch] medication compared to if you have to take medication three or four times a day," Blindauer said.
Parkinson's is caused by the loss of brain cells in the mid-brain region known as the substantia nigra. Those brain cells produce the neurotransmitter dopamine.
Without adequate dopamine levels, neurons can fire out of control, resulting in a lack of control of movement.
The most common symptoms are trembling; rigidity in the arms, legs and trunk; slowness of movement, such as while walking; and a lack of balance and coordination.
While there is no cure for the disease, several oral medications can help control symptoms, and most patients can maintain a high level of daily function throughout their lives, according to the National Parkinson Foundation.
Many Parkinson's patients are treated with the so-called gold standard combination of levodopa, which the brain converts into dopamine, along with carbidopa, a drug that helps control nausea and allows for a higher dose of levodopa.
The new drug used in the study, rotigotine, is among a class of drugs known as dopamine agonists, which mimic the effects of dopamine in the brain.
About 1.5 million Americans have Parkinson's disease, which tends to be more common among people older than 60, according to the foundation.
Dosing of drugs long has been a problem for Parkinson's patients, said Erwin Montgomery, a professor of neurology and director of the movement disorders program at the University of Wisconsin, Madison.
"With a lot of [oral] medications, they just go up and down in the bloodstream too quickly," he said.
It is believed that the cyclical variation in drug levels also contributes to motor complications and a weakening of the effectiveness of the drugs.
This year, Titan Pharmaceuticals, in a National Institutes of Health-sponsored study, reported promising results from a monkey trial using a device that is implanted under the skin to release a Parkinson's drug over a period of six months.
Time-release oral medications also have been tried, but even those do not produce perfect results, he said. The idea of a patch has potential advantages, Montgomery said.
"We can bypass the mouth and stomach by applying a patch," he said. "It does give us other options."
However, he said, a potential disadvantage of a patch is that it makes it more difficult to regulate drug levels throughout the day, which sometimes is necessary.
For instance, some patients take a pill every hour while others take one every eight hours, he said. And those intervals can change over periods as short as six months to a year.
"You really are at the mercy of the time control of the patch," he said. Eventually, a patch might be found to work best in combination with an oral medication, he said.
The study, which involved 242 patients, appeared in this month's issue of the Archives of Neurology. Funded by Schwarz Pharma Inc., maker of rotigotine, it compared various doses of the drug through a patch to a placebo patch.
Researchers found that the transdermally administered rotigotine achieved results similar to those of two other oral dopamine agonists based on a traditional Parkinson's scoring system.
However, because the patch was compared with a placebo, it is not known how it would compare in a head-to-head trial with orally administered Parkinson's drugs.
The patch drug also resulted in at least one "adverse" event, such as nausea, vomiting, fatigue and drowsiness, during the 14-week trial in 91 percent of patients.