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PPE Drugs - Neuro > Drugs for Parkinson's, Myasthenia Gravis, Dementia > Flashcards

Drugs for Parkinson's, Myasthenia Gravis, Dementia Flashcards

1
Q

Name 6 drugs/drug classes which are used in the treatment of Parkinson’s. Give an example where relevant

A

1) Levodopa
2) Dopamine receptor agonists - e.g. Apomorphine
3) Monoamine oxidase type B inhibitors - e.g. Selegiline
4) Cathechol-O-methyl transferase (COMT) inhibitors - e.g. Entacapone
5) Anticholinergics - e.g. Procyclidine
6) Amantidine

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2
Q

Why do you not give dopamine as a treatment for Parkinson’s?

A

Cannot cross the blood-brain barrier

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3
Q

Why do you give levodopa alongside a decarboxylase inhibitor?
Name one

A

Inhibits peripheral aromatic amino acid decarboxylase, meaning the levodopa you give cannot be converted to dopamine before it has crossed the BBB.
Carbidopa

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4
Q

How does Levodopa cross the BBB?

A

Via a large neutral amino acid transporter

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5
Q

Why does the effect of Levodopa decrease as Parkinson’s disease progresses?

A

Can only be converted to dopamine inside dopaminergic neurones of the substantia nigra - hence requires some to still be present. Therefore cannot work when most have been destroyed

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6
Q

What is the mechanism of action of Levodopa?

A

Increases dopamine concentration in the brain - hence reduces inhibition on the thalamus, which in turn increases excitation of motor cortex.

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7
Q

What is a major problem with Levodopa administration?

A

Vast majority deactivated in the gut/periphery - only around 1% reaches CNS

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8
Q

Give 4 ADRs of Levodopa

A

Nausea
Drowsiness
Confusion
Hypotension

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9
Q

What is the “on-off effect” of Levodopa?

A
  • Patient’s symptoms get worse towards end of dosing interval, so you give higher dose
    BUT
  • This results in dyskinesias (i.e. excessive involuntary movements) at the beginning of the dosing period
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10
Q

List 3 drug interactions associated with Levodopa

A
  • Vit B6 increases peripheral breakdown
  • MAOIs risk hypertensive crisis
  • Antipsychotic drugs block dopamine receptors, so produce Parkinsonism
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11
Q

Give 3 examples of Dopamine receptor agonists

A

Apomorphine
Bromocriptine
Ropinirole

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12
Q

When are dopamine receptor agonists used over levodopa?

A

In earlier stage Parkinson’s

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13
Q

How are Ropinirole and Apomorphine administered?

A

Ropinirole - oral

Apomorphine - SC injection

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14
Q

What is one unusual side effect of the dopamine receptor agonists?

A

Impulse control disorders - e.g. gambling

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15
Q

Compare the benefits/risks of levodopa vs dopamine receptor agonists

A

DRAs have relatively fewer ADRs, especially motor ones, but lower efficacy and expensive

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16
Q

Name a monoamine oxidase type B inhibitor

A

Selegiline

17
Q

What is the mechanism of action of MAOIs?

A

MAO metabolises dopamine in the gut and brain, hence by inhibiting this enzyme you increase the amount of dopamine reaching the brain

18
Q

What are the benefits and disadvantages of using MAOIs alongside levodopa?

A
  • Good because increases effects of Levodopa and means lower dose can be used
    BUT
  • May lead to hypertension due to increased catecholamines and hence symp. drive
19
Q

What sort of drug is Entacapone?

A

COMT inhibitor

20
Q

How are COMT inhibitors used?

A

Only alongside levodopa

21
Q

What is the mechanism of action of COMT inhibitors?

A
  • Inhibits the COMT pathway of dopamine breakdown

- Therefore increases central uptake of levodopa, and decreases levodopa dose needed

22
Q

Give 4 ADRs of COMT inhibitors

A
  • Diarrhoea
  • Postural hypotension
  • Nausea
  • Hallucinations
23
Q

Give an example of an anticholinergic drug used in Parkinson’s

A

Procyclidine

24
Q

What is the mechanism behind anticholinergic use in Parkinson’s?

A
  • Query usefulness, but thought that ratio between ACh and dopamine must be maintained - decreasing ACh increases dopamine transmission
25
Q

List some ADRs of anticholinergic drugs

A

Think “SLUDGE”

  • Salivation
  • Lacrimation
  • Urination
  • Defaecation
  • GI cramps
  • Emesis
26
Q

List some drugs which may exacerbate myasthenia gravis

A
  • Aminoglycosides
  • B blockers
  • Succinylcholine
  • ACE inhibitors
27
Q

Give 2 broad mechanisms by which myasthenia gravis is treated

A
  • Immunosuppression

- Acetylcholinesterase inhibitors

28
Q

Give 2 examples of acetylcholinesterase inhibitors used in myasthenia gravis

A

Pyridostigmine

Neostigmine

29
Q

Which other condition are AChE inhibitors used to treat?

Name some examples relevant to this condition

A

Dementia

Donepezil, Galantamine

30
Q

Give some ADRs of AChE inhibitors

A
  • Anticholinergic such as SLUDGE
  • Bradycardia –> falls
  • Peptic ulcers
  • Worsening of COPD
31
Q

What is the class/mechanism of action of Memantine?

A

NMDA antagonist

32
Q

Give some ADRs of Memantine

A
  • Hypertension
  • Dyspnoea
  • Headache
  • Dizziness

PPE Drugs - Neuro (5 decks)

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