antidepressants Flashcards

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1
Q

dep theory – monoamine deficit theory

A

○ Deficit in monoamine neurotransmitters (NA and 5HT) cause depression

○ Evidence: reserpine (inhibit NA and 5HT) storage ==> depressed mood

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2
Q

Limitations of theory

A
  • Hypothesis formulated for NA but later emphasis shift from NA –> 5HT
  • Monoamine markers in depressed pt yield inconsistent and equivocal results
  • Inadequate to explain all pharmacological actions in depression
      * Monoamines impt but there are complex interactions with other neurotransmitter systems as well
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3
Q

9 classes of antidep

A
  • MAO Ai (reversible)
  • TCA
  • SSRI
  • SNRI
  • NDRI (bupropion)
  • NaSSA (mirtazapine)
  • melatonin receptors (agomelatine)
  • Serotonin antagonist and reuptake inhibitor (trazodone)
  • multimodal serotonergic antidep (vortioxetine)
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4
Q

MAOi eg

A

moclobemide (safest, reversible MAOi-A)

phenelzine (MAO-i A > B)
tranylcypromine (MAO-i A,B)
selegiline (MAOi-B)

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5
Q

types of MAO enzymes

A
  • MAO-A
    □ 5HT broken down mainly by specific enzyme
    □ NA and dopamine
  • MAO-B
    □ NA and dopamine
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6
Q

MAOi/ RIMA MOA

A

incr biological availability of monoamines
* MAO-A, MAO-B preference
□ affects the conc of neurotransmitters recycled from being degraded by MAO

(A: incr for all 5HT,NA,DA)
(B: more specific for NA,DA)

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7
Q

RIMA indication

A
  • depression (reversible , less SE > older gen)
  • social ANX d/o
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8
Q

ADR for MAOi

A
  • Postural hypotension (DA)
    • Sympathetic block produced by accumulation of dopamine in cervical ganglia (neck)
    • Acts as inhibitory transmitter, not activated quick enough to respond to change in BP
    • HYPERTENSIVE CRISIS (NE)
  • Restlessness and insomnia, ANX, arrhythmia
    • Due to CNS stimulation
  • Serotoninergic function
    • Not combined with other drugs enhancing serotoninergic function (pethidine)
      ○ Hyperexcitability, incr muscular tone
      ○ myoclonus (jerk, involuntary movements)
      ○ Loss of consciousness
      ○ seizure
      (weight gain, sexual dysfuction)
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9
Q

DFI for MAOi

A
  • Concomitant intake of too high in tyramine (cheese, cured meats, conc yeast pdt)
    ○ NA SE: Acute hypertension, severe throbbing headache, intracranial hemorrhage
    ○ MAOi prevent break down of monoamines (tyramine), excess tyramine = sympathomimetic effect
      - Tyramine uptake by adrenergic terminals, compete with NA for vesicular compartment
      - Incr displacement and release of NA into synapse
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10
Q

DDI more likely in___ MAOi

A

irreversible, non-selective MAOis > reversible, MAO-A selective (moclobemide)

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11
Q

DDI for MAOi

A

Serotonin syndrome

  • DDI with serotonergic drugs = incr serotoninergic activity
  • Tremor, hyperthermia, CVS collapse
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12
Q

TCAs MOA

A

1st gen monoamine reuptake inhibitor antidep

2nd gen has milder SE, improved compliance
(nortriptyline > amitriptyline, imipramine)

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13
Q

types of TCAs + eg

A

1) non-selective for SERT/ NET – 5HT, NA
(imipramine, amitriptyline, nortriptyline, Clomipramine)

2) selective for NET – NA
(desipramine)

both on presynapse, feedback inhibition pathway

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14
Q

TCA metabolism

A

amitriptyline (3) –> nortriptyline (2 amine)
imipramine (3) –> desipramine (2)

2*: lower anticholinergic, sedation & cardiotoxic SE

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15
Q

TCA indication

A
  • depression
  • Clomipramine (2nd line for OCD)
  • amitriptyline (neuropathic pain, migraine prophy)
  • nortriptyline (neuropathic pain)
    * late preg
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16
Q

ADR of TCAs

A
  • Sedation
    • H1
    • Tolerance to sedation can develop in 1-2 wks
  • Postural hypotension
    • a1
  • Dry mouth, blurred vision, constipation
    • Parasympathetic effect (M1)
  • 5HT3 block: GIT & sexual dysfunction
  • seizure, QTc prolong (arrhy), weight gain
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17
Q

DDI w/ TCAs

A

Serotonin syndrome
* DDI with other drugs that incr serotoninergic activity
* Tremor, hyperthermia, CVS collapse

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18
Q

SSRI MOA

A
  • Greater 5HT reuptake selectivity than TCAs
  • 50-1000x selectivity for 5HT > NA
    * minimal effect/ reuptake of NE, DA
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19
Q

SSRI eg

A
  • Fluoxetine (50x selective for 5HT) —-> norfluoxetine
  • Citalopram (1000x 5HT selective)/ escitalopram
  • fluvoxamine
  • sertraline
  • paroxetine
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20
Q

indication of SSRI

A
  • Depression
  • eating d/o: fluoxetine,
  • OCD: fluoxetine, fluvoxamine, sertraline
  • ANX: escitalopram, paroxetine
  • Panic: citalopram, sertraline
  • Sertraline (BF, post MI depression)
21
Q

advantage of SSRI compared to TCAs

A

1) safer in overdose, less SE (better compliance)
a. TCA > MAOi > SSRI (death per px)
2) Better tolerance than TCAs
a. Improved ADR, better compliance
b. lack affinity for (A1: CVS effect)/ (H1: sedation)/ (M1: anticholinergic dry mouth, constipation)

3) Efficacy

22
Q

ADR of SSRI

A
  • Nausea, Insomnia (trough, b. dose)
    * esp fluoxetine
  • headache, transient nervousness (initiation)
  • seizure, bleeding risk, hypoNa (SIADH), EPSE
  • GI & Sexual dysfunction (5HT3)
  • Sedating effect (H1)
23
Q

specific eg of SSRI ADR

A
  • Fluoxetine (4-6hr)
    * norfluoxetine (4-16d) long t1/2, insomia
  • Citalopram / escitalopram
    * QTc prolongation
  • paroxetine
    * MOST anticholinergic, sedate, weight gain, short t1/2, withdrawl sx
24
Q

serotonin syndrome

A

potentiation of action in central and peripheral NS
(serotonergic drug + MAOi/ another serotonergic)

  • neuromuscular hyperactivity
    (ANX, agitation, confusion, clonus, hyperreflexia, muscle rigidity, unexplained FEVER –> CVS collapse)
25
Q

SNRI MOA

A
  • Similar to dual 5HT & NA reuptake inhibition ~ non-selective TCAs
    • May have additional receptor antagonism
      • Monoamine reuptake inhibitor (5HT & NA), weak (DA)
26
Q

SNRI eg

A

Venlafaxine —> Desvenlafaxine
Duloxetine

27
Q

SNRI indication

A
  • Depression
  • Generalised ANX disorder: venlafaxine, duloxetine
  • DM neuropathy, stress urinary incontinence, fibromyalgia, chronic MSK pain
    • Duloxetine structure resembles panadol
28
Q

SNRI specific ADR

(5HT3 antagonist, hypoNa, bleed risk, EPSE)

A
  • venlafaxine: incr BP, seizure
  • duloxetine: urinary hesitation
    * avoid in hep and renal insuff
29
Q

ADR of SNRI compare to SSRI

A
  • Serotoninergic ADR (similar to SSRI)
    • Nausea, insomnia, sexual dysfunction
  • Withdrawal effects more common and stronger than SSRI and TCA
30
Q

NaSSa (tetracyclic) MOA

A

mirtazapine = Noradrenergic and specific serotonergic antidepressant

  • NA (a2 autoreceptor) and 5HT2c receptor antagonist
  • incr NE and 5HT
  • (and) Antagonist 5HT2,3. H1, M1
31
Q

NaSSa ADR

A
  • H1 receptor (sedation)
  • A1 (orthostatic hypotension)
  • Somnolence, incr appetite, weight gain
32
Q

benefits of NaSSa

A
  • Reverse GI and sexual SE of SSRI/ SNRI
  • used in elderly, less SIADH effect
  • breastfeeding (risk vs benefits)
  • fewer DDI (nor primarily CYP)
33
Q

NDRI MOA

A

bupropion
norepinephrine-dopamine reuptake inhibitor

  • does not inhibit MAO or the reuptake of 5HT
  • 3 metabolites (inhibit NE)
34
Q

NDRI indications

A

Depression
Smoking cessation (suppress craving)

35
Q

NDRI ADR

A
  • Seizure ++++
  • QTc
  • Insomnia
  • Psychosis
  • not for eating d/o (alr at risk of ion imbalance, if on bupropion, can lead to seizure
  • decr sexual SE of SSRI/ SNRI
36
Q

PK of NDRI

A

T1/2: 10-21hr
Active metabolites (incr alertness, worsen insomnia ON)
- Hydroxybupropion
- Threohydrobupropion
- Eerythrohydrobupropion

37
Q

benefits of NDRI

A

Decr SE of SSRI/ SNRI
Smoking cessation aid
obese pts

38
Q

avoid BUP in

A
  • eating d/o
  • underweight
  • seizure
  • tamoxifen therapy (CYP2D6i)
  • preg
39
Q

melatonin receptor agonist MOA

A

agomelatine

  • agonist of melatonin MT1, MT2 receptors
  • antagonist of 5HT2C receptor (incr release NE, DA)
40
Q

ADR of MRA

A

Sedation
GI
Incr LFT (avoid in hep insufficiency)

  • has less bleeding risk
41
Q

DDI of MRA

A

fluvoxamine, ciprofloxacin

(strong CYP1A2 inhibitors: incr MRA dose)

42
Q

SARI

A

trazodone
* 5-HT2A antagonist/reuptake inhibitors
* Blocks reuptake of 5HT
* Antagonise 5HT2a, H1, a1 adrenoreceptor

43
Q

indication of SARi

A

Depression

Insomnia (off-label) ***

44
Q

ADR of SARI

H1, A1, 5HT3, bleed, SIADH, EPSE

A
  • sedation
  • orthostatic hypotension
  • QTc

Rare SE: priapism (long erection)

45
Q

SMS MOA

A
  • serotonin multi-modulator and simulator
    VORTIOXETINE

agonist activity 5HT1A
partial agonist activity 5HT1B
antagonism 5HT1D, 5HT7, 5HT3

46
Q

vortioxetine therapeutic effects

A

has several identified mechanisms
(5HT agonist, partial agonist, antagonist)

  • further release of 5HT and other neurotransmitters (DA, NE, Ach, H) in brain (prefrontal cortex, hippocampus)
47
Q

vortioxetine ADR

(SMS)

A

pro-cognitive effects
- risk of suicidal thoughts or actions
- similar as SSRI (hypoNa, GI, sexual, bleeding risk)

48
Q

ketamine MOA

A

glutamate NMDA receptor antagonist

49
Q

ketamine indication

A
  • rapid onset antidep effect (nasal spray – tx-resistent dep + SSRI/SNRI)
  • anesthetic (IV)