Welcome to pharmacology by Lecturio. My name is Dr. PJ Shukle.
We are going to be covering Parkinson's disease and other
movement disorders and the drugs that we use to help control
them. The dopamine hypothesis of how the brain works is quite
interesting. Reduced dopamine levels are seen in patients with
Parkinson's disease. So quite naturally we as physicians want to
increase those levels. So we give dopamine agonist. We give
dopamine agonist to these patients with Parkinson's disease
to mitigate their symptoms but long term exposure to these
medications results in increasing schizophrenic type symptoms
and mania and psychotic symptoms. We know also that treatment
of schizophrenia involves reducing dopamine levels. So you can see
that there is a reaction and an interaction between Parkinson's
disease and schizophrenia and mania. And the Chinese recognized
this 2000 years ago when they recognized that Parkinson's
disease type syndromes and psychotic diseae type syndromes
were a Yin and Yang kind of relationship. Drugs used to treat
psychosis and hyperactivity rely on reducing the levels of dopamine
and dopamine transmission in the brain. And drugs used to treat
Parkinson's disease and dyskinesias, rely on increasing
those very same levels. Drugs used to treat Parkinson's
disease can include dopamine precursors like levodopa,
dopamine agonists, MAO inhibitors, and COMT inhibitors. Drugs
used to treat other diseases include diseases like tremor, Wilson's disease,
complex choreas, Huntington's disease, and Tourette's syndrome.
Let's take a look at the brain. Now we already looked at this
very same diagram when we were looking at our psychotic medication.
So the effects of increasing dopamine are quite important.
In the nigrostriatal tract, you improve extrapyramidal function
and this causes an improvement in Parkinsonian symptoms. The same
medications in the mesocortical and mesolimbic tracts cause
apathy and lack of emotion; and hallucination and delusion.
In the TI tract, this will stimulate prolactin release. So
patients who are on these medications may have hyperprolactinemia.
And in the fourth pathway, you are effecting the chemoreceptor
trigger zone. That houses the vomiting center of the brain
and causes anorexia, nausea and vomiting. So these are
important side effects of the medications that we use to treat