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PR3153 > IC8 Pharmacology of antidepressants & antipsychotics > Flashcards

IC8 Pharmacology of antidepressants & antipsychotics Flashcards

1
Q

What is the main components involved in antidepressants & antipsychotics?

A

In depression, serotonin is lacking.
Antidepressants help to stimulate & increase production of serotonin.

In psychosis, there is too much dopamine. Anti-psychosis are often blockers that reduces dopamine levels.

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2
Q

What are the 2 classes of antidepressants?

A

Antidepressants (I)
- MAOIs & tricyclic antidepressants (TCAs)

Antidepressants (II) [Our focus in this IC]
- SSRIs, selective noradrenaline uptake inhibitors, & non-selective 5-HT/NA uptake inhibitors

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3
Q

Why is depression so significant that it is considered as a problem?

A
  1. Major cause of work days lost to disability
  2. Major cause of premature death
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4
Q

What are the symptoms of depression?

A

Misery, apathy (lack of interest), pessimism, low self-esteem, indecisiveness, loss of motivation, loss of libido

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5
Q

What is the monoamine theory?

A

The monoamine theory states that:
- Depression is caused by monoamine neurotransmitters.

However, this theory is no longer used. It is believed that there are other factors that can cause depression, not just monoamine neurotransmitters.

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6
Q

What are the 2 forms of monoamine oxidase (MAO)?

A

There are 2 major forms of MAO:
1. MAO-A
2. MAO-B

      - 5-HT is mainly broken down by MAO-A.

      - Both MAO-A and MAO-B helps to breakdown noradrenaline (NA) & dopamine
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7
Q

What is the MOA of monoamine oxidase inhibitor (MAOi)?

A

MAOi helps to block MAO, increasing 5-HT, NA and dopamine concentration.

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8
Q

Name an example of a MAOi

A

Phenelzine

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9
Q

What is the ADR of MAOis?

A
  1. Postural hypotension
  2. Restlessness & insomnia due to CNS stimulation
  3. Should not be combined with other drugs that enhances serotoninergic function
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10
Q

What is a major drug food interaction in MAOis?

A

MAOis are not to be taken with cheeses.

Cheeses have tyramine. MAOis lead to accumulation of tyramine.

Tyramine will then compete with noradrenaline in the resulting in sympathomimetic effect.

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11
Q

What is the MOA of tricyclic depressants (TCAs)?

A

Tricyclic antidepressants (TCAs) prevent the reuptake of monoamine (e.g. serotonin, noradrenaline, dopamine)

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12
Q

What are examples of TCAs that we need to know?

A

SERT: serotonin transporter
NET: Norepinephrine transporter

Non-selective for SERT/NET:
Imipramine, amitriptyline, nortriptyline

Selective for NET:
Desipramine

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13
Q

Nortriptyline VS Amitriptyline

A

Amitriptyline is a 1st generation TCA

Nortriptyline is a 2nd generation TCA.

Nortriptyline has milder side effects and better compliance.

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14
Q

What are the common ADRs of TCAs?

A
  1. Sedation
  2. Postural hypotension
  3. Dry mouth, blurred vision, constipation

H1 receptor antagonism is associated w sedation.

a-adrenoceptor sympathetic block leads to postural hypotension

Muscarinic receptor antagonism leads to dry mouth, blurred vision and constipation

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15
Q

What is the MOA of selective serotonin reuptake inhibitors (SSRIs)?

A

SSRIs are drugs that selectively inhibits the reuptake of serotonin. This increases serotonin activity, which can help reduce depression.

SSRIs are much more selective for 5-HT as compared to TCAs. This makes SSRIs superior to TCAs

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16
Q

What are some examples of SSRI?

A

Fluoxetine, citalopram

Fluoxetine is the most commonly prescribed antidepressant.

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17
Q

What are the 3 advantages of SSRIs?
1. Affinity for a-adrenoceptors
2. Effect on histamine receptors
3. Affinity for muscarinic cholinergic receptors

A

SSRIs have:
1. Low affinity for a-adrenoceptors - ↓ CV effects
2. Lack of effect at histamine receptors - ↓ sedation
3. Low affinity for muscarinic cholinergic receptors - ↓ anticholinergic SE

Overall, SSRIs are safer in overdose and SSRIs having less SE will lead to better compliance.

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18
Q

What are the ADRs of SSRIs?

A
  1. Nausea
  2. Insomnia
  3. Sexual dysfunction
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19
Q

What are 3 possible ADRs when SSRI is taken with other drugs that increases serotonergic activity (e.g MAOIs)?

A
  1. Tremor
  2. Hyperthermia
  3. Cardiovascular collapse
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20
Q

What is the common duration that a patient should be on antidepressants?

A

Antidepressants should be taken for 6 months to 2 years

21
Q

What is the MOA of Serotonin and Noradrenaline reuptake inhibitors (SNRIs)?

A

SNRIs have similar MOA to non-selective TCAs, where they inhibit the uptake of both 5-HT and NA reuptake.

22
Q

What are examples of SNRIs?

A
  1. Venlafaxine
  2. Desvenlafaxine
23
Q

Comparing SSRIs to SNRIs, which is 1st line and which is 2nd line for antidepressants?

A

SSRIs are 1st line antidepressants. SNRIs are 2nd line antidepressants.

24
Q

What is the advantage of venlafaxine as compared to TCAs?

A

Venlafaxine has fewer adverse effects than TCAs

25
Q

What are the ADRs of SNRIs?

A

The ADRs of SNRIs are similar to SSRIs.
1. Nausea
2. Insomnia
3. Sexual dysfunction

26
Q

What is psychosis?

A

Psychosis refers to a collection of symptoms that affect the mind, where there has been some loss of contact with reality.

Psychosis is often caused by over dopamine reactions.

27
Q

What is schizophrenia?

A

Schizophrenia is a serious chronic mental illness that affects how a person thinks, feels, and behaves.

Schizophrenia onset often takes place in late adolescence / early adulthood

People with schizophrenia may seem like they have lost touch with reality, which can be distressing for them and for their family and friends.

Psychosis is a major cause of schizophrenia.

28
Q

What are the 5 symptom domains of schizophrenia?

A
  1. Positive symptom*
  2. Negative symptom*
  3. Aggressive symptom
  4. Cognitive symptom
  5. Anxiety/depression

Our focus is mainly on positive & negative symptoms

29
Q

What are examples of positive symptoms?

A
  1. Delusions
  2. Hallucinations
  3. Thought disorder
  4. Abnormal behaviours

Positive symptoms are usually the most disturbing to others and often result in referral to psychiatrist & detection of schizophrenia.

30
Q

What are examples of negative symptoms?

A
  1. Withdrawal from social contacts
  2. Flattening of emotional responses
31
Q

What is one possible reason that is speculated to cause schizophrenia?

A

Neurodevelopmental disorder

32
Q

What are the 3 theories that explains a patient’s positive symptoms?

A
  1. Dopamine theory
  2. 5-HT theory
  3. Glutamate theory
33
Q

All antipsychotic drugs are _______ antagonist

A

D2 antagonist

34
Q

What are the 6 antipsychotic drugs that we need to know?

A
  1. Chlorpromazine
  2. Haloperidol
  3. Amisulpride
  4. Clozapine
  5. Olanzapine
  6. Risperidone
35
Q

What are the 4 pathways of dopamine in the brain?

A
  1. Nigrostriatal
  2. Mesolimbic
  3. Mesocortical
  4. Tuberoinfundibular
36
Q

These 3 pathways are part of the 4 pathways of dopamine:
1. Nigrostriatal pathway
2. Mesocortical / mesolimbic pathways

Which pathway is our target to block dopamine in?

A

Our target is the mesocortical / mesolimbic pathways.

The nigrostriatal pathway is involved in voluntary movement control. If we block this pathway, it can lead to loss of control of voluntary movement, resulting in parkinsonian disease symptoms.

If we block the tuberoinfundibular pathway, it will also lead to ADR.

In schizophrenia, dopamine increases in the mesocortical / mesolimbic pathways. Hence, we want to block this pathway.

37
Q

Classify the 6 antipsychotics that we need to know into
(1) Typical antipsychotics - aka 1st generation
(2) Atypical antipsychotics - aka 2nd generation

  1. Chlorpromazine
  2. Haloperidol
  3. Amisulpride
  4. Clozapine
  5. Olanzapine
  6. Risperidone
A

Typical antipsychotics (1st generation):
1. Chlorpromazine
2. Haloperidol

Atypical antipsychotics (2nd generation):
1. Amisulpride
2. Clozapine
3. Olanzapine
4. Risperidone

Both typical and atypical antipsychotics are used to control positive symptoms of schizophrenia.

38
Q

What are the differences between typical antipsychotic drugs and atypical antipsychotic drugs?

A

Typical antipsychotics produce more extrapyramidal side effects (EPS) as compared to atypical antipsychotics.

Typical antipsychotics only block D2 receptors.
Atypical antipsychotic blocks both serotonin and D2 receptor.

39
Q

What are extrapyramidal side effects (EPS)?

A
  1. Acute dystonias
  2. Tardive dyskinesia & akathisia

Acute dystonias - involuntary muscle contractions in either sustained or intermittent patterns that lead to abnormal movements or postures. Due to blockage of D2 receptors in the nigrostriatal pathway.

Tardive dyskinesias (TDs) - are involuntary movements
Akathisia - an inability to remain still

40
Q

Which part of the brain is involved in the extrapyramidal pathway?

A
  1. Basal ganglia
  2. Striatum
  3. Substantia nigra
41
Q

When we think about antipsychotic drugs, we think about whether they affect the a-adrenoceptors, muscarinic receptors, and the H1 histamine receptors.

Chlorpromazine affects all 3 receptors.

What are the side effects of chlorpromazine?

A
  1. Postural hypotension, dizziness
  2. Dry mouth, constipation, blurred vision
  3. Sedation, weight gain
42
Q

Haloperidol only has effects for a-adrenoceptors.

What are the SE of haloperidol?

A

Haloperidol only has postural hypotension and dizziness side effects.

As the muscarinic and histamine receptors are not affected, there are no dry mouth, constipation, blurred vision, sedation, weight gain side effects.

43
Q

What is the most ADR of clozapine?

A

Agranulocytosis

44
Q

Most atypical antipsychotics inhibit:
1. a-adrenoceptors
2. Muscarinic receptors
3. H1 histamine receptors

What are the side effects associated with atypical antipsychotics?

A
  1. Postural hypotension, dizziness
  2. Dry mouth, constipation, blurred vision
  3. Sedation, weight gain
45
Q

Amisulpride is an atypical antipsychotic.

Why does Amisulpride have lesser side effects than the other atypical antipsychotics?

A

Amisulpride is more selective for D2 receptors and it does not block a-adrenoceptors and H1 histamine receptors

Amisulpride can cause gynecomastia in males as it increases prolactin secretion.

46
Q

Which atypical antipsychotic can induce diabetes?

Atypical antipsychotics (2nd generation):
1. Amisulpride
2. Clozapine
3. Olanzapine
4. Risperidone

A

Drug-induced diabetes can be caused by:
1. Clozapine
2. Olanzapine
3. Risperidone

47
Q

Which atypical antipsychotic can induce weight gain?

Atypical antipsychotics (2nd generation):
1. Amisulpride
2. Clozapine
3. Olanzapine
4. Risperidone

A

Drug-induced weight gain can be caused by:
1. Clozapine
2. Olanzapine
3. Risperidone

48
Q

Why do atypical antipsychotics produce less extrapyramidal side effects (EPS)?

A

There are many types of serotonin and dopamine receptors.

Atypical antipsychotics are more selective for the types of serotonin and dopamine receptors that have lesser EPS.

E.g: By ↓ antagonism w D1, it will result in lesser EPS.

Note: Our target is D2 receptors and not D1.

49
Q

What are the additional benefits of atypical antipsychotics as compared to typical antipsychotics?

A

Only clozapine, olanzapine, risperidone have these effects:
1. More effective against negative symptoms
2. Better at mood stabilization

PR3153 (18 decks)

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