Part 6: LBD and PD Drugs

We could call this blog and the next one “The Balancing Act” because they are about two groups of drugs whose actions are polar opposites of each other. Today’s blog is about PD drugs. Next week’s will be about dementia drugs. Be sure to read both blogs—they go together but there was just too much information for a single blog.

No drug will cure PD or LBD—or any other neurological disorder for that matter. However, they do treat the symptoms and that adds to one’s quality of life. Both groups are well known to LBD families, especially those with PDD, where the dementia was preceded by the motor problems of Parkinson’s disease.

Lewy bodies attack brain cells and extract chemicals the brain cells use to transmit information (neurotransmitters).  In the mid-brain, they remove dopamine, needed for good motor functioning. In the cerebral cortex, they target acetylcholine, needed for good mental functioning. These two chemicals operate on a ratio system. If the level of acetylcholine is higher than that of dopamine, the body acts as though the dopamine level is too low—with poor motor functioning. Conversely, if the level of dopamine is higher, the body acts as though the acetylcholine level is too low—with poor cognitive functioning.

PD meds that are too strong will improve mobility but decrease cognition.







Dementia meds that are too strong will improve cognition but decrease mobility.


Drugs used to treat PD act to change the dopamine/acetylcholine ratio in four ways:

Dopamine replacement: Sinemet has been the most commonly used PD drug for years. It effectively controls motor symptoms with few short-term side effects. However, its long terms side effects such as muscle rigidity and confusion can be serious.

Dopamine copying or mimicking: Requip, Mirapex and Neupro are in a newer group called dopamine agonists.  They cause fewer long term problems and are now usually prescribed first with Sinemet added, if needed, for better control.  Short term side effects include increased confusion and hallucinations. These drugs are not recommended for anyone with dementia.

Dopamine preservation: The following drugs all act in various ways to preserve the level of dopamine in the cells.  Physicians usually prescribe these weaker drugs to boost the effectiveness of Sinemet.

Symmetrel has side effects include increased psychiatric symptoms and anxiety. It is not recommended for anyone with psychiatric symptoms (or LBD-related symptoms such as hallucinations or delusions.)

Eldepryl and Azilect are new, still controversial, drugs. They don’t appear to have any serious cognitive side effects.

Tasmar and Comtan are drugs that inhibit a chemical that helps to move dopamine out of the brain cells. They do not appear to have any serious cognitive side effects.

Acetylcholine blocking: Cogentin and Artane are anticholinergics that maintain the balance by blocking acetylcholine and preventing it from being effective. Motor functioning may improve, cognitive symptoms will likely increase.  These drugs are rarely used today.

The bottom line is that PD drugs strong enough to improve motor function tend to increase dementia symptoms. Next week’s blog will explain how dementia drugs strong enough to treat dementia may increase PD symptoms. Families and physicians usually have to look for a happy medium, giving up some mobility to maintain cognition or vice versa. Most families opt for more cognition.

The authors of this blog are not physicians. We report what we and other caregivers have learned by experience, from physicians and from the literature. This blog is informational only. You should always talk with a physician about individual issues.