Dopamine Pharmacology

List 4 ways that dopaminergic tone can pharmacologically be increased in the brain
> increasing DA tone

-activating DA Rs with bromocriptine, pramipexole, ropinirole

-causing DA release with amantadine, amphetamine

-preventing DA degradation with MAO inhibitor selegiline, rasagiline or COMT inhibitors (tolcapone and entacapone)

-preventing DA reuptake with benztropine, amantadine, cocaine, ritalin, bupropion

list 5 consequences of increased brain dopaminergic tone
> psychosis, schizophrenia, mania (limbic forebrain)

>reward for addictive behaviors (nucleus accumbens)

>choreoathretosis, Tourette, tics (striatum)

>nausea, vomiting (CRTZ)

>inhibition of prolactin release (pituitary gland)

5 consequences of decreased brain dopaminergic tone
>antipsychotic effect

>prevention or treatment of addiction

>parkinsonism

>antiemetic

>galatorrhea

Briefly diagram the acetylcholine-dopamine balance in the striatum and explain why anticholinergic drugs would be helpful in treating Parkinson’s disease; list 3 anticholinergic drugs used for this purpose and their side effects
Normal: Ach is in balance with DA; normal tone and movement

In Parkinson, there is too much ACh activity and or too little DA activity.

Therefore to treat parkinsons disease, is to increase DA tone or decrease ACh tone; this is accomplished with antimuscarinic drugs

AntiAch drugs
mAChR blockers:
Trihexypehnidyl
Benztropine
Amantadine

Side effects of AntiAch Drugs
Dry Mouth, eyes
Blurred vision
urinary retention
constipation
Hallucination
Sedation

Levodopa
used to increase DA levels
L-Dopa is converted into DA > activation of the DA Rs
Typically given with carbidopa to prevent conversion to DA in the periphery (less side effects)
Short T1/2 so must be given constantly
Efficacy only if there are DA neurons left

side effects: nausea and vomiting, choreoathetosis as disease progresses because there is too much dopamine or increased DA R sensitivity

Carbidopa
Given with L dopa because it inhibits peripheral decarboxylase that converts L Dopa into DA because too much circulating DA will cause nausea, emesis

Selegline
selective MAO B inhibitor > less food, drug interaction

prevents DA degradation

Tolcapone and Entacapone
COMT inhibitors
Tol crosses the BBB, Ent does not
Used with L-dopa and carbidopa to prevent CNS and peripheral degradation, increasing their efficacy

Bromocriptine
D2 receptor agonist > increased DA tone
side effects: see general increase DA tone side effects
was used to treat excessive prolactin release but not anymore due to ties to stroke + MI

Pramipexole and Ropinirole
New D2 receptor agonist
side effects: same as bromo, less frequent

Antiparkinsonism cocktail
L Dopa has a short half life and causes nausea and vomiting

To prevent frequent administration, anti MAOs and anti COMT are used (selegiline, rasagiline, tolcapone, entacapone)
to decrease peripheral side effects, carbidopa is used

List 4 actions of amanatine that may explain why it is useful in treating Parkinson’s disease
block nmda receptors
anti Ach
inhihbit DA uptake
causea DA release
antiviral

A-methyl-dopa Use: HTN, Opioid Withdrawal. Mechanism: A2 agonist, decreases sympathetic outflow, inhibits NE release, rebound HT. SE: dry mouth, sedation. Note: A-methyl-dopa is metabolized to A-methyl-NE (A2 agonist) Cocaine Inhibits neuronal uptake, can cross into CNS. I: amphetamines, CA Always …

B/C many of the drugs (carbidopa-levodopa & Requip (ropinirole) can cause hypotension Why should you be sure to include a supine and standing BP? Demerol Selegiline (Eldepryl) & rasagiline (Azilect) contraindications? WE WILL WRITE A CUSTOM ESSAY SAMPLE ON ANY …

-progressive neurodegenerative disorder -associated with degeneration of neurons that release dopamine in the brain and an imbalance between dopaminergic and cholinergic neurotransmission -leads to motor symptoms of tremor, rigidity, postural instability, and slowed movement parkinson’s disease medication class overview: -dopamine …

Levodopa (Dopar, Larodopa) Notes – Minimal amount reaches the brain, half life = 60-90 minutes (3-6 doses/day) – Onset of action: several months – Activates dopamine receptors (↑dopamine) across BBB (cannot administer dopamine) Levodopa (Dopar, Larodopa) Side Effects a. dose …

Patients who have bradykinesia usually experience loss of automatic movements such as blinking of eyes, arm swinging when walking and swallowing of saliva. These are movements which occur automatically and the person is not aware of their occurrence. Bradykinesia affects …

The patient with Parkinson’s disease who has been positively responding to carbidopa-levodopa (Sinemet) suddenly develops a relapse of symptoms. Which explanation by the nurse is appropriate? “This is called the ‘on-off phenomenon.’ Your health care provider can change your medication …

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