Patients With Parkinson’s 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 may 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.

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, and 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 coauthor Carl E. Clarke, MD, 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.”

The review appears in the The Cochrane Library. This review assessed data from 44 randomized trials involving 8,436 participants. The authors caution, however, that the studies compared each class of drugs against placebo, rather than conducting “head-to-head” comparisons of each class against the others.

This leaves open the possibility that the findings arose not from actual differences in the treatments, but rather from other factors such as differences in the types of people included in the various trials. A large trial featuring direct comparisons of the three drug classes currently is underway in the United Kingdom, Clarke says.

Source: Health Behavior News Service