Parkinson’s Patients More Likely to Stick With Certain 'Add-On' Drugs

Of the three main types of oral drugs commonly added to levodopa therapy for patients with advanced Parkinson’s disease, one might be the most effective, according to a new review.

People with Parkinson’s disease often initially experience tremors, stiffness, slowed movement or difficulty with balance and coordination. These symptoms result from the destruction of brain cells that produce dopamine – an important chemical that transmits nerve impulses.

Many people with Parkinson’s start treatment by taking levodopa, which the body converts to dopamine. After a time, however, levodopa alone is not always enough.

The three classes of drugs for add-on treatment are dopamine agonists, which stimulate dopamine receptors in the brain, drugs known as COMT inhibitors and MAOB inhibitors, which slow the breakdown of dopamine in the body.

Of these, dopamine agonists might be most effective, according to a new review.

The irony for patients and doctors alike is that while all of the add-on drugs help improve functional motor skills, they simultaneously might increase numerous other side effects such as dyskinesia, dizziness, sleep disturbances, nausea, constipation and even hallucinations.

Although the risk of side effects increased with all three types of add-on drugs, patients were most likely to continue treatment when they were taking dopamine agonists. This class includes medications such as pramipexole (Mirapex), ropinirole (Requip), cabergoline (Dostinex) and bromocriptine (Parlodel).

“There’s a tendency to think that stronger drugs give more adverse effects, but we didn’t find that with dopamine agonists,” says review co-author Carl E. Clarke, M.D., a neurologist at the University of Birmingham in England. “They seem to be as well tolerated as the other classes, so the results are quite positive in terms of using the agonists ahead of the other two.”

Parkinson’s disease is a chronic, progressive disorder affecting more than 6 million people worldwide, making it the most common degenerative condition of the brain after Alzheimer’s disease. Both illnesses are most common in the elderly, so with an aging U.S. population, their prevalence is likely to increase.

“No treatments have been proven to slow progression of the disease,” said William J. Weiner, M.D., director of the Maryland Parkinson’s Disease and Movement Disorders Center at the University of Maryland Medical Center. “Yet with treatment to alleviate motor symptoms, most patients can function extremely well for six to 10 years.”

Levodopa typically controls symptoms very well for up to five years, but eventually a patient’s symptoms start to reappear each day before the next dose is due – or symptoms might reappear and disappear unpredictably. Patients might also develop dyskinesia, which results in uncontrollable jerking and writhing movements.