"Progress is being made to expand our use of medications, develop new medications and to treat symptoms that either we haven't been able to treat effectively or we didn't realize were problems for patients," said Dr. Robert Hauser, professor of neurology and director of the University of South Florida Parkinson's Disease and Movement Disorders Center in Tampa.
Parkinson's disease, a degenerative brain disorder, affects more than 1 million Americans. It destroys nerve cells in the brain that make dopamine, which helps control muscle movement. Patients experience shaking or tremors, slowness of movement, balance problems and a stiffness or rigidity in arms and legs.
In one study, Hauser evaluated the drug droxidopa (see the structure right), which is not yet approved for use in the United States, to help patients who experience a rapid fall in blood pressure when they stand up, which causes light-headedness and dizziness. About one-fifth of Parkinson's patients have this problem, which is due to a failure of the autonomic nervous system to release enough of the hormone norepinephrine when posture changes.
Hauser studied 225 people with this blood-pressure problem, assigning half to a placebo group and half to take droxidopa for 10 weeks. The drug changes into norepinephrine in the body.
Those on the medicine had a two-fold decline in dizziness and lightheadedness compared to the placebo group. They had fewer falls, too, although it was not a statistically significant decline.
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In a second study, Hauser assessed 420 patients who experienced a daily "wearing off" of the Parkinson's medicine levodopa (see structure left), during which their symptoms didn't respond to the drug. He compared those who took different doses of a new drug called tozadenant, which is not yet approved, with those who took a placebo. All still took the levodopa.
At the start of the study, the patients had an average of six hours of "off time" a day when symptoms reappeared. After 12 weeks, those on a 120-milligram or 180-milligram dose of tozadenant (see structure below) had about an hour less of "off time" each day than they had at the start of the study.
Tozadenant, which works on brain receptors thought to regulate motor function, merits further study in future trials, Hauser said.
In another study, Hauser looked at 321 patients with early stage Parkinson's whose symptoms weren't handled well by a medicine called a dopamine agonist, typically the first drug prescribed for Parkinson's patients. During the 18-week study, Hauser assigned them to take either their usual medicine plus an add-on drug called rasagiline (brand name Azilect see below structure) or their usual medicine and a placebo.
Azilect is approved for use in patients with early stage disease as a single therapy or as an add-on to levodopa, Hauser said, but not yet as an add-on to dopamine agonists.
Those taking the Azilect but not those taking the placebo improved by 2.4 points on a standard Parkinson's disease rating scale.
Costs of the still unapproved drugs are not known. Azilect costs about $200 monthly at the 1-milligram daily dose used in the study.
Each of the studies was funded by the pharmaceutical company making the particular drug: Chelsea Therapeutics paid for the blood-pressure study; Biotie Therapies Inc., supported the "wearing-off" study; and Teva Pharmaceutical Industries sponsored the Azilect study. Hauser is a consultant for all three companies.
