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Pharmacology - Fall > Lecture 12 - Parkinson's Disease > Flashcards

Lecture 12 - Parkinson's Disease Flashcards

1
Q

At what age do symptoms of Parkinson’s disease generally appear?

A

Around age 60

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2
Q

What are the symptoms of Parkinson’s disease?

A
  • Rhythmic tremor - often occurs at first in one hand, resembles “pill rolling”
  • Leaning forward or backward when upright
  • Muscle rigidity - pushing on an arm causes it to move in jerky increments instead of smoothly
  • Difficulty rising from a sitting position
  • Speech*
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3
Q

What are marker’s of Parkinson’s disease?

A
  • Muscle rigidity
  • Slow movements
  • Loss of spontaneous movements
  • Resting tremor, first in one hand
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4
Q

Which motor pathways control voluntary movement?

A
  • Upper motoneurons
  • Lower motoneurons
  • Corticospinal pathways
  • Pyramidal tracts
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5
Q

Which motor pathways control involuntary movement?

A
  • Extrapyramidal system
  • Basal ganglia
  • Reticular system
  • Vestibular system
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6
Q

What is the neuropathophysiology of Parkinson’s disease?

A
  • Loss of neurons in substantia nigra causing loss of dopamine innervation of striatum
  • Balance btwn acetylcholine and dopamine is lost causing abnormal signalling and impaired mobility
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7
Q

At what stage of neuron loss do symptoms of Parkinson’s disease generally appear?

A

When about 70% of nigrostriatal neurons are lost

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8
Q

What normally inhibits and excites GABA neurons?

A
  • Inhibited by dopamine

- Stimulated by acetylcholine

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9
Q

Which symptoms of Parkinson’s disease are controllable by drug therapy?

A
  • Bradykinesia (slow initiation of movement)
  • Tremor at rest
  • Muscle rigidity
  • Abnormal posture
  • Early treatment for “neuronal sparing”
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10
Q

What are the pharmacological targets of drugs for Parkinson’s disease?

A
  • Increase dopamine signalling in corpus striatum and substantia nigra
  • Decrease cholinergic activity
  • Decrease peripheral dopamine effects at D1/D2 dopamine receptors
  • Decrease peripheral L-DOPA metabolism
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11
Q

What is the function of COMT w/ respect to dopamine synthesis in substantia nigra?

A

Catalyzes L-DOPA -> 3-OMD

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12
Q

What is the function of DDC (dopa decarboxylase) w/ respect to dopamine synthesis in substantia nigra?

A

Catalyzes L-DOPA -> dopamine

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13
Q

What is the function of TH (tyrosine hydroxylase) w/ respect to dopamine synthesis in substantia nigra?

A

Catalyzes tyrosine -> L-DOPA

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14
Q

What does the D1 subfamily of dopamine receptors do?

A

Increases cAMP

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15
Q

What does the D2 subfamily of dopamine receptors do?

A

Decreases cAMP

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16
Q

What are first line drugs to treat the early stage of Parkinson’s disease?

A
  • MAO-B inhibitors (rasagiline, selegiline)

- Levodopa (levodopa/carbidopa or levodopa/benserazide)

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17
Q

Does L-Dopa cross the BBB?

A

Yes, but only 1% enters the brain, causing side effects in the periphery

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18
Q

Where is L-Dopa metabolized?

A

Intestine, blood, and peripheral tissues

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19
Q

What are the therapeutic effects of L-Dopa?

A
  • Reduces rigidity and bradykinesia
  • Improves motor function and speech
  • Return of facial expression
20
Q

What is the first choice drug for improving motor dysfunction from Parkinson’s disease?

A

L-Dopa

21
Q

What is the most common side effect of L-Dopa that causes people to discontinue use of the drug?

A

Dyskinesias (abnormal involuntary movements)

22
Q

What are some side effects of L-Dopa besides dyskinesias?

A
  • Nausea, vomiting
  • Hypotension and cardiac arrhythmias
  • Wearing off
  • “On-off” effect
  • Insomnia, confusion
  • Psychosis, hallucinations
23
Q

What does carbidopa do?

A
  • Inhibits dopa decarboxylase (DDC) or aromatic L-amino acid decarboxylase (AADC)
  • Prevents breakdown of L-Dopa in periphery and allows more to cross BBB
24
Q

What are common adjunct therapies w/ L-Dopa?

A
  • L-Dopa and carbidopa = Sinemet

- L-Dopa and benserazide = Prolopa

25
Q

What is entacapone used to treat?

A
  • Later stage Parkinson’s disease

- Used to treat problems associated w/ long term therapy of L-Dopa (wearing off, on-off effects)

26
Q

What does entacapone do?

A
  • Selective and reversible inhibitor of peripheral COMT causing reduction of peripheral metabolism of L-Dopa
  • Causes increased conversion of L-Dopa to dopamine in the brain
27
Q

Does entacapone cross the BBB?

A

No

28
Q

What is a disadvantage to entacapone?

A

Cause enhance adverse effects of L-Dopa like dyskinesias, nausea, psychosis, and confusion

29
Q

What is entacapone normally used w/ and when?

A
  • Sinemet (L-dopa + carbidopa) and entacapone = Stalevo

- Common use in pxs who have been on L-Dopa for over 10 years

30
Q

What is amantadine?

A

Dopamine releaser

31
Q

What are the therapeutic effects of amantadine?

A
  • Increases dopamine release in CNS

- Reduce dyskinesia

32
Q

When is amantadine used?

A
  • Short term (under 6 months)

- Sometimes used w/ L-Dopa

33
Q

What are the side effects of amantadine?

A

Similar to L-Dopa

34
Q

What are ropinirole and pramipexole?

A

Selective dopamine agonists at D2/D3 receptors

35
Q

What are the therapeutic effects of ropinirole and pramipexole?

A
  • Act on D2 and D3 receptors in and outside of corpus striatum
  • Improves depressive symptoms
  • May be combined w/ L-Dopa to treat “on-off” effects
36
Q

What are side effects of ropinirole and pramipexole and how can they be improved?

A
  • Dyskinesia b/c act on D2 receptors outside of corpus striatum (dyskinesia is a result of peaks and troughs of drug delivery, so a patch will level out drug delivery and decrease dyskinesia)
  • Suppresses prolactin secretion
  • Hypotension
  • Visual and auditory hallucinations
37
Q

What are some muscarinic antagonists used for Parkinson’s disease treatment and what do they do?

A
  • Trihexyphenidyl HCl
  • Benzatropine mesylate
  • Selective for muscarinic acetylcholine type 1 receptor
38
Q

What are the therapeutic effects of muscarinic antagonists?

A

Tremors, but not rigidity (generally used in young px w/ severe tremor)

39
Q

What is a contraindiction of trihexyphenidyl HCl and benzatropine mesylate?

A

Glaucoma

40
Q

What does monoamine oxidase A do?

A

Metabolizes NE and serotonin

41
Q

What does monoamine oxidase B do?

A

Metabolizes dopamine

42
Q

What is selegiline?

A

Irreversible MAO B inhibitor

43
Q

What does selegiline enhance the effects of?

A

L-Dopa

44
Q

What are side effects of selegiline?

A

Insomina and cognitive problems

45
Q

What occurs if selegiline is superceded by rasagiline?

A
  • Less production of amphetamine-like by-products
  • Better bioavailability
  • Useful in px w/ depression and/or cognitive decline
46
Q

What are some non-pharm therapeutics to treat Parkinson’s disease?

A
  • Surgery - ablation and/or deep brain stimulation (to inhibit STN and reduce dyskinesia)
  • Growth factors
  • Stem cells - replacement of dopaminergic neurons

Pharmacology - Fall (15 decks)

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