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PR3153 > IC14 Pharmacology III Parkinson's & Alzheimer's disease > Flashcards

IC14 Pharmacology III Parkinson's & Alzheimer's disease Flashcards

1
Q

What is Parkinson’s disease?

A

It is a neurodegenerative disease that causes extrapyramidal motor symptoms due to striatal dopaminergic deficiency.

Examples of EPS are:
- Tremors
- Rigidity
- Bradykinesia

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2
Q

What are the 4 motor symptoms of Parkinson’s Disease?

A
  1. Tremor at rest
  2. Bradykinesia - slowness of movement
  3. Rigidity
  4. Gait disturbance and postural instability
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3
Q

What is the theorized pathophysiology of Parkinson’s disease?

A
  1. Failure to clear toxic proteins(a-synuclein)
  2. Resulting in accumulation of Lewy bodies
  3. Apoptosis of brain neuronal cells
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4
Q

What are possible treatments for Parkinson’s Disease?

A
  1. Levodopa
  2. COMT inhibitors (entacapone OR tolcapone)
  3. MAO-B inhibitors (selegiline OR rasagiline)
  4. Dopamine agonist (pramipexole)
  5. Amantadine
  6. Anticholinergics (trihexyphenidyl)
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5
Q

What is the pathway of dopamine synthesis?

A

L-tyrosine → Levodopa → Dopamine

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6
Q

Comparing levodopa and dopamine, which of the 2 can pass through the blood brain barrier?

A

Levodopa can pass through the blood brain barrier.

Dopamine is not able to pass through the blood brain barrier.

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7
Q

How do we treat Parkinson’s disease?

A

We give patients Levodopa.

Levodopa is often given together with carbidopa or benserazide.

Carbidopa and benserazide helps to block the dopamine enzymes, allowing more levodopa to reach the brain.

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8
Q

What are the side effects of levodopa?

A

The side effects of levodopa are:
1. Dyskinesia
2. N&V
3. Postural hypotension

Dyskinesia - involuntary, erratic, writhing movements of the face, arms, legs or trunk.

If a patient were to develop dyskinesia after using levodopa, it is permanent and does not go away once it develops.

Hence, while levodopa is highly effective, we would like to try other alternatives before starting patients on levodopa.

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9
Q

What is the MOA of COMT inhibitors?

A

COMT inhibitors help to block COMT from converting dopamine/levodopa to an inactive form.

Examples of COMT inhibitors:
- Entacapone
- Tolcapone

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10
Q

How are COMT inhibitors used?

A

They are often used as adjunct to levodopa.

They help to increase more available levodopa that enters the brain.

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11
Q

What are the side effects of COMT inhibitors?

A
  1. Dyskinesia - ↑ abnormal movements
  2. Liver dysfunction - associated w Tolcapone
  3. Nausea, diarrhoea
  4. Daytime sleepiness, sleep disturbances
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12
Q

What is the MOA of MAO-B inhibitors?

A

MAO-B inhibitors help to inhibit monoamine oxidase B, preventing the breakdown of dopamine.

Examples of MAO-B inhibitors:
- Selegiline
- Rasagiline

Selegiline can be used as 1st line monotherapy for early stages of Parkinson’s disease symptoms.

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13
Q

What are the SEs of MAO-B inhibitors?

A
  1. GI: Heartburn, loss of appetite
  2. Anxiety, palpitation, insomnia
  3. Nightmares, visual hallucinations

Hallucinations can be caused by too much dopamine. MAO-B inhibitors can lead to too much dopamine and this can trigger visual hallucinations.

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14
Q

What is an example of dopamine agonist & what is its MOA?

A

An example of a dopamine agonist:
- Pramipexole

MOA of dopamine agonists:
- Act directly on dopamine receptors in the brain to reduce symptoms of PD

Effects of dopamine agonists are still not superior to levodopa. Levodopa is still the GOLD standard.

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15
Q

Why do we use dopamine agonists instead of starting levodopa in younger pt w PD?

A

Despite levodopa being more efficacious, we are afraid of the development of dyskinesia.

Once dyskinesia develops, it is permanent. Hence, we use dopamine agonist in younger PD pt to reduce the risk of developing dyskinesia.

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16
Q

What are the SEs of dopamine agonists?

A
  1. N&V
  2. Postural hypotension
  3. Headache
  4. Dizziness
  5. Cardiac arrhythmia
  6. Sedation
  7. Somnolence
  8. Daytime sleepiness
17
Q

What is amantadine?

A

Amantadine is an antiviral drug that has mild antiparkinsonian effect (dyskinesia, tremor, etc.)

18
Q

How is amantadine given to a patient?

A

It is often given as monotherapy or adjunct to levodopa.

19
Q

What is the MOA of amantadine?

A
  1. It helps to enhance the release of stored dopamine.
  2. It functions as a dopamine agonist
  3. It is an anti-glutamate agent
20
Q

What is the special property of amantadine?

A

It is able to help reduce dyskinesia in pt w PD.

However, it does not completely eliminate dyskinesia.

21
Q

What are the side effects of amantadine?

A
  1. Difficulty concentrating
  2. Hallucination
  3. Insomnia
  4. Nightmares
  5. Livedo reticularis*

Livedo reticularis - venule swelling due to thromboses. It causes discolouration of limbs, while being able to see veins on the surface of the skin.

22
Q

What is an example of anticholinergics & how is it used?

A

Example of anticholinergic:
- Trihexyphenidyl - brand name: Benzhexol

Anticholinergic agents may be used as monotherapy or adjunct therapy to levodopa.

23
Q

What are anticholinergic agents used for?

A

It can be used to treat tremors, stiffness and sialorrhoea.

Sialorrhoea - a debilitating symptom which occurs when there is excess saliva in the mouth beyond the lip margin.

24
Q

What are the side effects of anticholinergics?

A
  1. Dry mouth
  2. Sedation
  3. Constipation
  4. Hallucination
  5. Delirium
  6. Confusion
  7. Urinary retention
25
Q

What is Alzheimer’s Disease?

A

Alzheimer’s disease is a brain disorder that slowly destroys memory and thinking skills and, eventually, the ability to carry out the simplest tasks.

26
Q

What is the process of signal transmission via acetylcholine?

A

Acetylcholine is made of acetate and choline.

When acetylcholine is released from the pre-synapse into the synaptic cleft, acetylcholinesterase (AChE) helps to break down acetylcholine into acetate and choline.

The choline is then recycled.

27
Q

What is the main class of drug used in treatment of Alzheimer’s disease?

A

Acetylcholinesterase inhibitors are the mainstay of Alzheimer’s disease treatment.

28
Q

What are the goals of therapy in Alzheimer’s disease management?

A
  1. Slow progression of disease
  2. Delay the need to institutionalization
  3. Improve QOL of patients and caregiver
29
Q

What are some examples of acetylcholinesterase inhibitors (AChEIs)?

A
  1. Donepezil
  2. Rivastigmine
  3. Galantamine
30
Q

Rivastigmine VS Galantamine

  1. What are the dosage forms available for the 2 AChEIs?
  2. Which has a longer half-life?
  3. How are both the drugs metabolised?
  4. What additional effect does galantamine have over rivastigmine?
A
  1. What are the dosage forms available for the 2 AChEIs?
    - Rivastigmine - oral tablet & transdermal patch
    - Galantamine - oral tablet
  2. Which has a longer half-life?
    - Galantamine has a longer half-life
  3. How are both the drugs metabolised?
    - Galantamine is metabolised by the liver
    - Rivastigmine is metabolised by the kidneys
  4. What additional effect does galantamine have over rivastigmine?
    - Galantamine may also act on nicotinic receptors in the brain, which may contribute to its therapeutic effects.
31
Q

What are some side effects of AChEIs?

A

More common SE:
1. N&V
2. Diarrhoea

Less common SE:
1. Muscle cramp
2. Bradycardia
3. Loss of appetite
4. Increased gastric juice secretion

32
Q

Apart from acetycholinesterase inhibitors, what is another drug that is used to treat Alzheimer’s Disease?

A

Ans: Memantine

33
Q

What is the MOA of Memantine?

A

It is a non-competitive NMDA receptor antagonist

34
Q

What are the side effects of memantine?

A
  1. Hallucination
  2. Confusion
  3. Dizziness
  4. Headache
35
Q

Alzheimer’s disease pt can present with Behavioural & Psychological Symptoms of Dementia (BPSD).

What medications can be used to treat BPSD?

A
  1. Antidepressants (SSRIs - e.g. citalopram)
  2. Anxiolytics (benzodiazepines)
  3. Neuroleptics (atypical antipsychotics - e.g risperidone)
  4. Sleep medications

PR3153 (18 decks)

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