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Semester 4 - Clinical Pharmacology And Therapeutics > Neurology Clinical Pharmacology > Flashcards

Neurology Clinical Pharmacology Flashcards

1
Q

What is idiopathic parkinson’s disease?

A

neudegenerative disorder

Progressive clinical course

Motor symptoms improve with levodopa

Non-motor symtoms

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2
Q

What are the clinical features of Parkinsonism?

A

Tremor - low frequency, pill rolling tremor

Rigidity - lead pipe rigidity

Bradykinesia

Postural instability

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3
Q

What are the non motor manifestations of parkinson’s?

A 
Mood changes
Pain - starts asymmetrical
Cognitive change
Urinary change
Urinary symptoms 
Sleep disorder - REM sleep behaviour disorder
Sweating
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4
Q

What is the prognosis of PD after 15 years?

A 
94% dyskinesia
81% falls
84% cognitive decline - 50% hallucinations
80% somnolence
50% swallowing difficulty 
27% severe speech problems.
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5
Q

How do you diagnose ID?

A

Clinical features
Exclude other causes of Parkinsonism
Response to Treatment
Structural neuroimaging is normal

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6
Q

Describe the pathology of IPD?

A

Neurodegeneration

Lewy bodies - synucleinopathy

Loss of pigment - 50% loss before symptoms, increased turnover, upregulate receptors

Reduced dopamine

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7
Q

What is a DAT scan?

A 
Labelled tracer
Presynaptic uptake
Abnormal in PD
Not diagnostic
Tremor
Neuroleptic
Vascular
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8
Q

Describe the synthesis of catecholamines

A 
L-Tyrosine  (tyrosine hydroxylase)
L-DOPA (DOPA decarboxylase)
Dopamine (Dopamine B-Hydroxylase)
Noradrenaline (Phenylethanolamine n-methyltransferse)
Adrenaline
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9
Q

Why do we use L-DOPA and not dopamine?

A

As Dopamine cannot cross BBB

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10
Q

Describe the pharmacokinetics of levodopa

A

Oral administration

absorbed by AT - in competition with amino acids

90% inactivated in intestinal wall (monoamine oxidase and DOPA decarboxylase)

T1/2 = 2 hours so:
-Short dose internal (4x day)
fluctuations in blood levels and symptoms

9% converted to dopamine in peripheral tissues - DOPA decarboxylase

<1% enters CNS - competes with AA for AT across BBB.

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11
Q

What are the formulations of L-DOPA?

A

Dopamine is used in combination with a peripheral DOPA decarboxylase inhibitor:

  • Co-careldopa = Sinemet
  • Co-beneldopa = Madopar

This reduces the dosing required
Reduces side effects
Increases L-DOPA reaching the brain

Tablets only - standard dosage of variable strengths.

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12
Q

What are the advantages of L-DOPA?

A

Highly efficacious

Low side effects:
Nausea / anorexia - vomiting centres

Hypotension - central and peripheral

Psychosis - schizophrenia like effects - hallucinations / delusions / paranoia

Tachycardia

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13
Q

What are the disadvantages of L-DOPA?

A

Precursor - needs enzyme conversion

Long term - loss of efficacy
Involuntary movements 
Motor complications:
On/Off
Wearing off - need before next dose
Dyskinesias
Dystonia
Freezing
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14
Q

What are the interactions with L-DOPA?

A

B6 increases peripheral breakdown of L-DOPA

MAOIs risk hypertensive crisis

Many antipsychoticdrigs block dopamine receptors and parkinsonism is a side effect

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15
Q

What are dopamine receptor agonists?

A

A do novo, add on therapy.

e.g. Ropinirole, pramipexole (tablet), apomorphine (subcut, only for patients with severe motor fluctuations)

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16
Q

What are the advantages of DRAs?

A

Direct acting

Less dyskinesias / motor complications

Possible neuroprotection

17
Q

What are the disadvantages of DRAs?

A

Less efficacy than L-DOPA
Impulse control disorders
More psychiatric s/e dose limiting
Expensive

18
Q

What are impulse control disorders?

A 
Pathological gambling
Hypersexuality
Compulsive shopping
Desire to increase dosage
Punding
19
Q

What are the side effects of dopamine receptor agonists?

A 
Sedation
Hallocinations
Confusion
Nausea
Hypotension
20
Q

How does monoamine oxidase B work?

A

Metabolises dopamine
Predominates in dopamine containing regions in brain
MAOBi enhance dopamine.

21
Q

What are some examples of Monoamine oxidase B inhibitors?

A

Selegiline

Rasagaline

22
Q

Monoamine oxidase B inhibitors work?

A

Can be used alone or to prolong the action of L-DOPA.

Smooths out motor response
May be neuroprotective

23
Q

How do COMT inhibitors work?

A

It reduces the peripheral brakdown of L-DOPA to 2-O-Mythyldopa.

Only work with L-DOPA

Have an L-DOPA ‘sparing’ effect - it prolongs the motor response to L-DOPA and reduces the symptoms of ‘weaning off’

e.g. Entacapone - called ‘Stalevo’ when combined.

24
Q

Give examples of anticholinergics

A

Trihexyphenidydyl
Orphenadrine
Procyclidine

25
Q

What are the advantages of anticholinergics?

A

Treat tremor

Not acting via dopamine system

26
Q

What are the disadvantages of anticholinergics?

A

No effect on bradykinesia

Side effects:

  • Confusion
  • Drowsiness
  • Usual anticholinergics/e
27
Q

What is amantadine?

A

Mechanism of action uncertain maybe enhanced dopamine release or anticholinergic NMDA inhibition.

Poorly effective
Few side effects
Little effect on tremor

28
Q

What surgery can be used in Parkinsons?

A

Of value in highly selected cases - people who are dopamine responsive but have significant side effects with L-DOPA and o psychiatric illness.

Controlled trials

Lesion -thalamus for tremor and Globus Pallidus for dyskinesias

Deep Brain Stimulation - Subthalamic Nucleus

29
Q

What is Myasthenia Gravis?

A

Myasthenia gravis is a chronic autoimmune disease that affects neuromuscular signalling.

ACh is prevented from binding due to IgG at the receptor and so ACh is broken down by cholinesterase’s

Fluctuating fatiguability, weakness skeletal muscle

Extraocular muscles - commonest presentation
Bulbar involvement - dysphagia, dysphonia, dysarthria
Limb weakness - proximal symmetric
Respiratory muscle involvement

30
Q

What drugs exacerbate Myasthenia Gravis?

A

Drugs affecting neuromuscular transmission exacerbate Myasthenia Gravis.

Aminoglycosides
Beta-blockers, CCBs, quinidine, procainamide
Chloroquinine, penicillamine
Succinylcholine
Magnesium
ACE inhibitors ... lots more too!
31
Q

What can cause a crisis?

A

Acute exacerbation - Myasthenia crisis

Over-treatment - cholinergic crisis

Look exactly the same.

Treat by supporting respiration and swelling immediately.

32
Q

What drugs can be used to manage MG?

A

Acetylcholinesterase inhibitors

Corticosteroids - decrease immune response

Steroidsparing - Aathioprine

IV immunoglobulin

Plasmapheresis - removed AChR antibodies and short-term improvement.

33
Q

What do acetylcholinesterase inhibitors do?

A

Enhance neuromuscular trasnmission
Skeletal and smooth muscle
Excess dose can cause depolarising block - cholinergic crisis
Muscarinic side effects

34
Q

What is Pyridostigmine?

A

An anticholinergic.
It is taken orally.

Prevents breakdown of ACh in NMJ which makes ACh more likely to engage with remaining receptors.

Onset: 30mins, Peak: 60-120mins, Duration: 3-6hours.

Dose interval and timing is crucial.

35
Q

What are the side effects of pyridostigmine?

A 
Miosis and the SSLUDGE syndrome:
Salivation
Sweating
Lacrimation
Urinary incontinence 
Diarrhoea
GI upset 
Emesis
36
Q

What is neostigmine?

A

An anticholinergic

Oral and IV preparations.
Quicker action, duration up to 4 hours.
BUT, significant antimuscarinic side effects.

Semester 4 - Clinical Pharmacology And Therapeutics (26 decks)

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