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Dopamine Precursors and Agonists – Treatment of Movement Disorders

by Pravin Shukle, MD
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      Slides Parkinson Disease and other Movement Disorders CNS Pharmacology.pdf
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    Let's start with the drug levodopa. Why do we call it levodopa? Well, dopamine doesn't cross the blood brain barrier unfortunately. So we have to use the L-enantiomer of dopa, L-DOPA, or levodopa. L-DOPA enters the brain via L-amino acid transporters. So they are very specific transporters that actually actively move L-DOPA from outside the cell or outside the brain into the brain area. Toxicity of levodopa include anorexia, nausea and emesis. That just make sense because it's affecting the chemoreceptor trigger zone. Other symptoms include postural hypotension and tachycardia. And remember, that levodopa is contraindicated in patients who have psychosis because you are going to worsen the psychotic symptoms. What is carbidopa and why do we give it with levodopa? Well let's take a look at this reaction and interaction between drug and barrier. L-DOPA is broken down by tissue decarboxylases in the peripheral tissues. This causes side effects. So when you have breakdown of L-DOPA into dopamine, it causes side effects in the peripheral tissue. Carbidopa blocks DOPA decarboxylase. You get prolonged activity of action and more transmission and movement of L-DOPA into the brain. You also have fewer side effects peripherally. That's why we give carbidopa in association with levodopa. Let's talk about dopamine agonist, bromocriptine and pramipexole. Bromocriptine and other analogues are ergot alkaloids. They are partial D2 agonist, and they increase the activity of dopamine pathways. They may be used in combination with L-DOPA. The side effects of drugs like bromocriptine include nausea and vomiting through the CTZ, dyskinesia and confusion, and postural hypotension which I had mentioned before with L-DOPA. The ergot alkaloid related side effects that are specific to bromocriptine is pulmonary infiltrates and erythromelalgia. Erythromelalgia is a very unique kind of a skin reaction and you can see a women and her...

    About the Lecture

    The lecture Dopamine Precursors and Agonists – Treatment of Movement Disorders by Pravin Shukle, MD is from the course CNS - Pharmacology. It contains the following chapters:

    • Dopamine Precursors
    • Dopamine Agonists

    Included Quiz Questions

    1. Suicidal ideation
    2. Anorexia
    3. Nausea
    4. Emesis
    5. Tachycardia
    1. Psychosis
    2. Pregnancy
    3. Multiple sclerosis
    4. Depression
    5. Anxiety
    1. Bromocriptine: D2-Receptor Pramipexole: D3-Receptor
    2. Bromocriptine: D3-Receptor Pramipexole: D2-Receptor
    3. Bromocriptine: D2-Receptor Ropinirole: D3-Receptor
    4. Carbidopa: D2-Receptor Levodopa: D3-Receptor
    5. Diphenhydramine: D3-Receptor Pramipexole: D2-Receptor
    1. Bromocriptine
    2. Ropinirole
    3. Pramipexole
    4. Apomorphine
    5. Bupropion
    1. Carbidopa inhibits peripheral DOPA decarboxylase to reduce side effects.
    2. Carbidopa inhibits central DOPA decarboxylase to reduce side effects.
    3. Carbidopa helps transport levodopa into the central nervous system.
    4. Carbidopa pierces the blood brain barrier to allow levodopa to enter the central nervous system.
    5. Levodopa inhibits peripheral DOPA decarboxylase to reduce side effects.

    Author of lecture Dopamine Precursors and Agonists – Treatment of Movement Disorders

     Pravin Shukle, MD

    Pravin Shukle, MD


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