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CNS > L37 Antidepressant drugs > Flashcards

L37 Antidepressant drugs Flashcards

0
Q

What are the types of mood disorder?

A
  • Depression, Mania (monopolar)
  • Manic depression (bipolar= oscillate between high and low)
  • side effects of drug treatment is often depression, eg rimonabant (for obesity and inteferon alpha for hep C)
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1
Q

What are the symptoms of depression?

A

1) Emotional
- mood and thought disorder
2) Biological
- motivational impairments
3) Cognitive
- difficulty decision making and poor concentration
4) Psychotic
* drug treatments aim to improve mood and motivational impairments

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2
Q

What are the symptoms of mania and bipolar disorder?

A
  • sleep less, excessive enthusiasm and confidence
  • increased libido
  • behaviours inappropriate to circumstances

*drug treatments aim to control excessive oscillations between high and low mood

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3
Q

What causes depression?

A

1) chemical imbalance
- functional deficit in 5HT/ NA
2) Neurodegeneration
- Neural apoptosis and neuorgenesis
3) Immune response
4) Genes
5) Environment (Stress)

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4
Q

What are the treatments for depression?

A

1) Pharmacological
- enhance monoamine levels in CNS
by: monoamine re-uptake inhibitors; monoamine oxidase inhibitor; receptor antagonists
2) cognitive behavioural therapy
3) neurological interventions (only in severe depressive patients)

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5
Q

How to increase monoamine function in the CNS?

A

1) post-synaptic receptor agonist, eg Buspirone
2) pre-synaptic receptor antagonist, eg mirtazapine
3) monoamine oxidase enzyme inhibitors, eg moclobemide (reversible) ; phenylzine (irreversible)
4) re-uptake inhibitors, eg fluoxetine, venlafaxine

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6
Q

What are the classes of antidepressants?

A

1) Typical: tricyclic antidepressant and specific re-uptake inhibitors
2) Atypical: mixed uptake blockers and receptor blocking drugs
3) Mood stabilisers: lithium, anti-epileptic drugs, atypical antipsychotics

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7
Q

What are typical antidepressants?

A

=TCA and specific re-uptake inhibitors

  • Monoamine oxidase inhibitors, eg Iproniazid, moclobemide
  • Tricyclic antidepressants, eg imipramine, amitriptyline, clomipramine, despiramine
  • Selective Serotonin reuptake inhibitors, eg fluozetine, paroxtine, clitalopram
  • Selective NA reuptake inhibitors, eg Reboxetine
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8
Q

What are the atypical antidepressants?

A

= mixed uptake blockers and receptor blocking drugs

  • Serotonin-NA Reuptake Inhibitors eg venlafaxine
  • 5HT2 antagonist + SSRI eg Trazodone
  • 5HT2 antagonist + SNRI eg nefazedone
  • alpha 2 adrenoceptor and 5HT antagonist eg mianserin, mirtazapine
  • Melatonin agonist and 5HT2 antagonist eg agomelatine

** all show delayed onset and similar efficacy despite different modes of action

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9
Q

What are mood stabilisers?

A
  • lithium, anti-epileptic drugs, atypical antipsychotics
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10
Q

What is the food interaction with MAO inhibiters?

A
  • individuals who take irreversible MAO inhibitors cannot metabolise ingested amines eg tyramine. =high level in blood
  • tyramine displaces NA from its terminals leading to a sympathomimetic effect =acute hypertension
  • drugs like amphetamine will also cause this reaction in people taking MAO inhibitors
  • this interaction is observed with irreversible inhibitors such as phenylzine; not seen with reversible MAO inhibitors eg moclobemide
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11
Q

What are the drug interactions of MAO inhibitors with opioids?

A
  • Pethidine (opioid) will cause hyperpyrexia (elevation in body temp) with restlessness, coma and hypotension with MAO inhibitors
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12
Q

What are the MAO inhibitors used in anti-depression?

A
  • Iproniazid
  • it inhibits breakdown of monoamines (MAO is found in all tissues including GI tract)
  • MAO-A prefers 5HT; MAO-B prefers DA and NA
  • side effects: cheese reaction (tyramine)
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13
Q

What are the examples of MAO inhibitors?

A
  • iproniazid, phenelzine, tranylcypromine, moclobemide
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14
Q

What is the mechanism of tricyclic antidepressants?

A
  • block reuptake of monoamines ( mainly NA and 5HT)
  • some block alpha2 adrenoceptor
  • Side effects= cardiotoxicity (tachycardia, arrhythmia, hypothension) and there is a low therapeutic index
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15
Q

What are the examples of tricyclic antidepressants?

A
  • amitriptyline (NA/ 5HT), despiramine (NA) and clomipramine (5HT)
  • amitriptyline is now mainly used in pain management
16
Q

What are the examples of tricyclic antidepressants?

A
  • amitriptyline (NA/5HT)
  • desipramine (NA)
  • clomipramine (5HT)
  • amitriptyline is now mainly for pain managment
17
Q

What are the therapeutic effects that tricyclic antidepressants exert?

A
  • NA & 5HT reuptake inhibition

- alpha 2 adrenoceptor antagonists

18
Q

What are the side effects that tricyclic antidepressants exert?

A
  • Muscarinic antagonist
  • alpha 1 adrenoceptor antagonist
  • histamine antagonist
  • cadiotoxic
19
Q

Fluoxetine

A 
- serotonin specific reuptake inhibitor
= first line!
- moderate efficacy
- largest group of antidepressant prescribed
- side effects: serotonin specific
20
Q

Venlafaxine

A
  • serotonin and NA specific reuptake inhibitor (=mixed reuptake inhibitor)
  • moderate efficacy
  • at low dose= act as serotonin specific inhibitor; high dose= mixed serotonin and NA reuptake inhibitor
    = second line treatment for non-responders for fluoxetine
21
Q

Reboxetine

A
  • NA specific reuptake inhibitor
  • limited efficacy
  • muscarinic and NA side effects
22
Q

What are the advantages of using selective re-uptake inhibitors over the tricyclic antidepressants?

A
  • block the reuptake of NA/5HT or NA+5HT so reduce drug interactions, cholinergic effects, no food interaction AND LOW toxicity in overdose
  • but have 5-HT related side effects:
    nausea, anorexia, insomnia, sexual dysfunction
  • NA related side effects:
    insomnia, constipation, sweating, sympathetic effects eg tachycardia, anxiety, aggression
23
Q

What are the advantages using atypical antidepressants?

A
  • improve efficacy, onset of action and reduce side effects
24
Q

Venlafaxine

A
  • mixed NA and 5HT reuptake inhibitor
25
Q

Trazedone

A
  • selective sertonin reuptake inhibitor and 5HT2 antagonist
26
Q

Nefazodone

A
  • selective NA reuptake inhibitor and 5HT2 antagonist

* 5HT2 antagonist= reduce 5HT2 side effects

27
Q

Mirtazapine

A
  • NA and 5HT receptor antagonists
  • NA receptor antagonist= can increase release of NA because it binds to the autoreceptor so no NA can binds to it. This means it blocks the negative feedback mechanism
  • increase NA can stimulate more 5HT release
28
Q

Agomelatine

A
  • melatonin agonist and 5HT antagonist
29
Q

Why is there a delayed onset of clinical efficacy

A

-because it takes time for receptor adaptations, ie up/down regulation

30
Q

What is discontinuation syndrome?

A
  • it is where patients decided not to carry on with medication, usually present with moderate or severe symptoms
  • common with patients who take paroxetine; less common with fluoxetine
31
Q

What is the general guideline for treatment of depression?

A
  • 1st line: selective serotonin reuptake inhibitor/ mirtazapine
  • 2nd line: MAO inhibitors or mixed drugs

*Very severe/drug resistant: electroconvulsive shock therapy and then deep brain stimulation

32
Q

How does lithium

A
  • Lithium
    : replace Na+ reducing neuronal excitability (attenuates glutamate signalling)
    : alters signalling via effects on 2nd messengers
    : effects on gene expression
  • effective in controlling mania but potential toxicity
  • exact mechanism is unknown
33
Q

Valproic acid

A
  • weak inhibitor of GABA transaminase (prevent GABA breakdown) so increases inhibitory neurotransmitters on Na channels
34
Q

Carbamazepine

A
  • derived from TCA, induces use-dependent block of Na channels
35
Q

What are the antipsychotics drugs that are used for mood stabilising?

A
  • haloperidol when acute

- olanzapine in long term

36
Q

What is the treatment of bipolar?

A
  • acute= lithium/ carbamazepine; 2nd line= sodium valproate
  • prophylaxis (preventative): lithium, olanzapine; 2nd line= carbamazepine
  • antipsychotic drugs reduce manic symptoms in 1-2 days
37
Q

What are the other applications for antidepressant drugs?

A
  • selective serotonin reuptake inhibitors can also be used for:
    OCD, social phobia, panic disorder, anxiety disorder, eating disorder

CNS (15 decks)

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