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Y2 Pharmacology and Therapeutics > Anti-Parkinsonian drugs and neuroleptics > Flashcards

Anti-Parkinsonian drugs and neuroleptics Flashcards

1
Q

Explain the process of dopamine synthesis

A

L-tyrosine -> L-DOPA
Tyrosine hydroxylase (rate-limiting)
L-DOPA -> Dopamine
Dopamine decarboxylase

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2
Q

Explain the process of dopamine metabolism

A

Dopamine removed from the synaptic cleft by dopamine transport (DAT) and noradrenaline transporter (NET)

Monoamine oxidase A - MAO-A metabolises Dopamine, NEt and 5-HT
MAO-B - metabolises dopamine
COMT - metabolises all catecholamines, wide distribution

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3
Q

What are the major locations of the dopaminergic pathways

A

Nigrostriatal pathway
Mesolimbic pathway
Mesocortical pathway
Tuberofundibular pathway

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4
Q

Where is the nigrostriatla pathway and what does inhibition of it result in

A

Substantia nigra pars compacta (SNc) to the striatum.

Inhibition results in movement disorders

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5
Q

Where is the mesolimbic pathway

A

ventral tegmental area (VTA) to the Nucleus Accumbens (NAcc).

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6
Q

Where is the mesocortical pathway and what is its function

A

VTA to the cerebrum.

Important in executive functions and complex behavioural patterns.

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7
Q

Where is the tuberoinfundibulnar pathway and what doe inhibition lead to

A

Arcuate nucleus to the median eminence.

Inhibition results in hyperprolactinaemia

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8
Q

Describe the epidemiology of Parkinson’s

A

1-2% of individuals over 60 years old

Around 5% of cases are due to mutations in certain genes (e.g. SNCA, LRRK2)

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9
Q

What is the pathophysiology of Parkinson’s

A

Severe loss of dopaminergic projection cells in Substantia nigra
Lewy bodies + neurites - Found respectively within neuronal cell bodies + axons
Consist of abnormally phosphorylated neurofilaments, ubiquitin + alpha-synuclein

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10
Q

How does Parkinsons disease clinically present

A 
Motor symptoms (4 cardinal symptoms) - resting tremor, bradykinesia, rigidity, postural instability 
Autonomic nervous system effects - olfactory deficits, orthostatic hypotension, constipation
Neuropsychiatric - sleep disorders, memory deficits, depression, irritability
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11
Q

How is levodopa used in Parkinsons treatment

A

Rapidly converted to DA by DOPA decarboxylase (DOPA-D)
Can cross blood-brain barrier (BBB)
Peripheral breakdown by DOPA-D - Leads to nausea and vomiting

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12
Q

What are the long term side effects of levodopa

A

Dyskinesias + ‘on-off’ effects. NOT disease-modifying (same mortality)

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13
Q

Give example of adjuncts used in Parkinsons treatment

A

DOPA decarboxylase inhibitors: Carbidopa and Benserazide

COMT inhibitors: Entacapone and Tolcapone

Prevents peripheral breakdown of DOPA-D (nausea and vomiting)

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14
Q

Describe the pharmacokinetics of DOPA decarboxylase inhibitors

A

Carbidopa and Benserazide
Do not cross the BBB - prevents peripheral breakdown of levodopa
Reduce required levodopa dosage

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15
Q

How are COMT inhibitors used in Parkinsons treatment

A

Entacapone and Tolcapone

increase amount of levodopa in the brain

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16
Q

Which receptors can dopamine act on

A

D1,5(Gs linked) or D2-4 (Gi-linked) receptors

17
Q

What are the types of dopamine receptor agonists and give examples of each

A

Ergot derivatives (bromocriptine and pergolide)

Non-ergot derivatives (Ropinirole)

18
Q

Describe ergot derivative dopamine receptor agonists

A

Act as potent agonists of D2 receptors

Associated with cardiac fibrosis

19
Q

What are non-ergot derivative dopamine receptor agonists available as (admin)

A

Ropinirole also available as extended-release formulation

Rotigotine also available as a patch

20
Q

Give an example of Monoamine oxidase B (MAOB) inhibitors and describe its use

A

Selegiline (deprenyl) + Rasagiline
Reduce the dosage of L-DOPA required
Can increase the amount of time before levodopa treatment is required

21
Q

Which types of drugs are used in Parkinsons treatment

A

Dopamine replacement (Levodopa) -DOPA decarboxylase inhibitors
Dopamine receptor agonists
MAO-B inhibitors

22
Q

Describe the epidemiology of schizophrenia (proportion, onset of symptoms, countries with higher incidence, life expectancy)

A

Affects 1% of population and has genetic influence
Onset of symptoms: between 15-35 years
Higher incidence in ethnic minorities (eg Afro-Caribbean immigrants)
Life expectancy - 20-30 years < average

23
Q

What are the positive symptoms of schizophrenia

A

Increase in Mesolimbic dopaminergic activity
Hallucinations: Auditory and visual
Delusions: Paranoia
Thought disorder: Denial about oneself

24
Q

What are the negative symptoms of schizophrenia

A

Decrease Mesocortical dopaminergic activity
Affective flattening: lack of emotion
Alogia: lack of speech
Avolition/ apathy: loss of motivation

25
Q

Give examples of drugs used for schizophrenia treatment (separate by generations)

A

Chlorpromazine
Haloperidol

Clozapine
Risperidone
Quetiapine
Aripiprazole

26
Q

What is the mechanism of action of chlorpromazine and its side effects

A

Primary mechanism of action – possibly D2 receptor antagonism

High incidence - anti-cholinergic, especially sedation
Low incidence - extrapyramidal side-effects (EPS)

27
Q

What is the mechanism of action of haloperidol and its side effects

A

Very potent D2 antagonist (~ 50x more potent than chlorpromazine)
Therapeutic effects develop over 6-8 weeks
Little impact on negative symptoms

High incidence - EPS

28
Q

Describe clozapine

A

Most effective antipsychotic
Very potent antagonist of 5-HT2A receptors
Only drug to show efficacy in treatment resistant schizophrenia and negative symptoms

29
Q

What are the side effects of clozapine

A 
Potentially fatal:
Neutropenia
Agranulocytosis
Myocarditis
Weight gain
30
Q

What is the mechanism of action of risperidone and its side effects

A

Very potent antagonist of 5-HT2A and D2 receptors

More EPS and hyperprolactinaemia than other atypical antipsychotics

31
Q

What is the mechanism of action of quetiapine and its side effects

A

Very potent antagonist of H1 receptors

Lower incidence of EPS than other antipsychotics

32
Q

What is the mechanism of action of aripiprazole and its side effects

A

Partial agonist of D2 and 5-HT1A receptors
No more efficacious than typical antipsychotics

Reduced incidences of hyperprolactinaemia and weight gain than other antipsychotics

33
Q

What is the cause of the reduction in life expectancy in schizophrenic patients

A

due to lifestyle choices made by individuals who have schizophrenia. High rates of drug use, smoking and suicidal

Y2 Pharmacology and Therapeutics (34 decks)

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