Pharmacology of Parkinson's Disease

Reading all the fine print on those fact sheets that come with Parkinson's disease medications is confusing and boring, so I decided to use humor to try to explain it.  I got the idea of using farm references by the phonetic pronunciation of Pharmacology (FARM-a-college-ee).


Parkinson's disease is caused when certain neurons in our brain die and quit producing dopamine.  Low dopamine levels cause the signals from our brain to our muscles to get scrambled and produces the erratic movements. Okay, easy enough, just give us dopamine.  The solution sounds simple, but there is a catch: our bodies are very protective of what it lets in the barn (brain) and dopamine can't even get on the farm.  

Dopamine - stay out!!!

The scientists developed levodopa which can get on the farm, but by itself, levodopa causes intense nausea and vomiting and turns into dopamine and still can't get in the barn (brain).  The scientists found that by adding carbidopa to the levodopa, they could prevent it from becoming dopamine and quell the nausea.  Carbidopa is like a Judas Goat, it leads the levodopa past the guard dogs and right into the barn (brain). The combination of carbi/levodopa is called Sinemet.

Sneaks the dopamine in

The problem with Sinemet is that our bodies try to get foreign items out of our bloodstream.  It takes about 45 - 75 minutes from mouth to blood stream and then our efficient blood cleansing organs get rid of it about an hour later, so not much makes it into the barn (3% according to the experts).


The scientists went back to work and found out that if they added another drug called entacapone (Comtan), they could keep the Sinemet in our bloodstream longer and therefore more can be herded in to the barn known as your brain.  The brand name combination of Sinemet and Comtan is called Stalevo.

Herding more into the barn

Comtan has a wonderful side effect of making your urine turn bright yellow, orange or even brown.  This has a tendency to freak out the lab techs when they ask you to pee in a cup.  It is my own personal observation that this yellow stain also creeps into your saliva and perspiration and I am pretty sure that it is staining my teeth as well (just call me mellow yellow).


There is another class of drugs called dopamine agonists. These drugs aren't designed to replace the missing dopamine, they are designed to make the receptors that use dopamine work better without it. It's kind of like dangling a carrot in front of a donkey.  

Agonists act like a carrot and can cause you to act like a donkey

There are 2 main agonists: Ropinirole and pramipexole, known under the brand names of Requip and Mirapex. These drugs do such a good job of stimulating the receptors that they can cause dangerous obsessive or compulsive behaviors such as gambling, uncontrollable shopping or risky sexual activity.  IF you are taking an agonist, you need to be aware of these potentially life altering side effects and find someone you can trust to monitor you. On the up side, agonist's have also been tied to increased creativity.  People start writing poetry or take up painting when they had no interest prior.


Rasagiline (Azilect) and selegiline (Eldepryl) are other drugs that are used in Parkinson's and are in a class of medications called monoamine oxidase (MAO) type B inhibitors.  They work by increasing the amounts of certain natural substances in the brain and act similar to the agonists.  They are often prescribed to recently diagnosed Parkies in an attempt to delay prescribing the Sinemet.

There are many other drugs used to either treat the symptoms of Parkinson's or the side effects of the drugs we take to relieve our symptoms.  

Treatment of Parkinson's consists of easing our symptoms only.  None of the currently available medications will stop the progression or cure it.  Over time, Sinemet causes unpleasant side effects (Parkinson's Drugs Side Effects) and becomes less effective, requiring us to take higher and higher doses, so Doctor's try to reduce the amount of it we take or delay its usage.

The reason Sinemet loses its effectiveness is the brain needs healthy dopamine producing neurons to convert the levodopa into dopamine, and, as the disease progresses, there are less and less neurons to do the converting.


I wrote a song about Sinemet, well, just the lyrics, the music is borrowed.  Have a listen:

Clicking on colored words will open a new window and take you to a different story or link. 

Thank you for reading this story, I hope you enjoyed it. This is just one of a hundred stories in my book, Parkinson's Humor - Funny Stories about My Life with Parkinson's Disease. Please consider purchasing a copy from Amazon.com or your favorite online book seller. Thank you and have a Happy Parkie Day!