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PHAR324 > Antidepressants > Flashcards

Antidepressants Flashcards

1
Q

What are the physiologic factors in depression?

A

changes in receptor-neurotransmitter relationships in the limbic area
-serotonin, norepinephrine, dopamine
-decrease in functional balance of these NTs

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2
Q

What are the three mechanisms for alterations in the balance/function of neurotransmitters?

A

impaired synthesis of neurotransmitters
increased breakdown/metabolism of neurotransmitters
increased pump re-uptake of neurotransmitters

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3
Q

What are the classes of antidepressants?

A

SSRI
SNRI
TCA
MAOI
atypical antidepressants

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4
Q

What is the MOA of SSRIs?

A

inhibit SERT

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5
Q

Which two SSRIs must be known for the exam?

A

escitalopram
citalopram

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6
Q

What is the MOA of SNRIs?

A

inhibit SERT and NET

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7
Q

Which SNRI must be known for the exam?

A

venlafaxine

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8
Q

What is the MOA of TCAs?

A

inhibit SERT + NET + muscarinic receptors + a1 receptors + histamine receptors + Na+ channels
-also produce antiarrhythmic effects

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9
Q

Which TCA must be known for the exam?

A

amitriptyline

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10
Q

Which pump does desipramine prefer?

A

NET > SERT

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11
Q

What is the MOA of MAOIs?

A

inhibit MAO which breaks down NTs

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12
Q

Why are MAOIs last choice?

A

drug-drug interactions
drug-food interactions
-tyramine –> hypertensive crisis

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13
Q

Which MAOI must be known for the exam?

A

isocarboxazid

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14
Q

What is the feel good hormone?

A

dopamine
-released in cases of drug abuse or smoking

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15
Q

What is the atypical antidepressant?

A

bupropion

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16
Q

What is the MOA of bupropion?

A

inhibits DAT and NET

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17
Q

What is another use of bupropion besides depression?

A

smoking

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18
Q

What is bupropion toxicity associated with?

A

seizures and cardiac toxicity
-narrow therapeutic margin
-structurally similar to amphetamine

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19
Q

Which antidepressant class is the safest?

A

SSRI
-fewer significant adverse effects and less problematic in overdose than TCAs and MAOIs
-more fatalities reported with extremely larger doses or co-ingestants like benzos or ethanol
-fatality is rare
-SNRIs like venlafaxine = greater risk of mortality in overdose

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20
Q

Describe SSRI ADME.

A

absorption:
-tmax: 4-8h
distribution:
-PPB: 80-98%
-Vd: 10-40 L/kg
metabolism:
-CYP 2D6
elimination:
-t1/2: average of 15-35h
-numerous active metabolites
-mostly renally excreted

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21
Q

What is the PPB of escitalopram?

A

56%

22
Q

Which SSRIs are potentially more toxic in overdose?

A

citalopram and escitalopram
-dose dependent QT prolongation
-structurally different from other SSRIs

23
Q

What is serotonin syndrome?

A

excessive levels of serotonin
-diaphoresis, diarrhea, hyperthermia, mental status change, myoclonus
-occurs most frequently after use of combination of serotonergic xenobiotics or high doses of isolated serotonergic xenobiotics

24
Q

Which labs should be taken if experiencing SSRI toxicity?

A

ECG if citalopram, escitalopram, SSRI + co-ingestant
neuromuscular finding labs (CK, myoglobin, SCr)

25
Q

What is the management of SSRI toxicity?

A

symptomatic and supportive care
seizures: BZD
cardiac abnormalities: sodium bicarbonate
torsades de pointes: magnesium sulfate
serotonin syndrome: cyprohepatidine

26
Q

What is the MOA of sodium bicarbonate in SSRI toxicity?

A

increases in serum pH and extracellular sodium = increased electrochemical gradient across cardiac cell membranes

27
Q

What is the MOA of magnesium sulfate?

A

decreases acetylcholine in motor nerve terminals and acts on myocardium = slowed rate of SA node impulse formation = prolonged conduction time

28
Q

What is the MOA of cyprohepatidine?

A

competitive binding to serotonin receptor = cooling and treatment of muscular rigidity

29
Q

What is the role of decontamination in SSRI toxicity?

A

? SDAC
-most benefit within 1-2 h
-may use up to 4 h
no role for gastric lavage

30
Q

What is the role of elimination in SSRI toxicity?

A

no role for MDAC
-no role due to rapid absorption
no role for hemodialysis
-ineffective due to high PPB, Vd

31
Q

What is the key to successful management in TCA toxicity?

A

early identification
-hard to distinguish serious toxicity based on symptoms alone
-progression of clinical toxicity is unpredictable and may be rapid
-get an ECG!

32
Q

Describe TCA absorption.

A

well absorbed
tmax up to 12h in overdose
anticholinergic effect on gastric emptying
=delay emptying

33
Q

Describe TCA distribution.

A

highly lipophilic and widely distributed
-Vd = 10-50 L/kg
PPB: 85-98% (highly protein bound)
not a good candidate for hemodialysis

34
Q

How are TCAs metabolized?

A

multiple CYPs
metabolism is highly variable

35
Q

Why is TCA metabolism highly variable?

A

genetic polymorphisms in 2D6
influenced by concomitant ingestion of ethanol or coingestants that induce or inhibit 2D6

36
Q

What is a poor predictor of outcome in TCA toxicity?

A

dose ingested and plasma concentration

37
Q

What is essential with TCA toxicity?

A

early ECG

38
Q

Which symptoms of TCA toxicity show rapid progression?

A

cardiotoxic symptoms
-onset often within 2 hours of ingestion

39
Q

What is the main mechanism of TCA causing cardiotoxicity?

A

Na+ channel blocking = QRS prolongation

40
Q

Which body systems are impacted by TCA toxicity?

A

cardio
respiratory
CNS

41
Q

How is the severity of TCA toxicity best reflected?

A

by ECG, not serum levels

42
Q

At what point does the QRS show risk of cardiotoxicity?

A

> 100 ms

43
Q

What is the first line management for dysrhythmias caused by TCAs?

A

sodium bicarbonate

44
Q

What is the MOA of sodium bicarbonate for dysrhythmias caused by TCAs?

A

sodium load: helps overcome Na+ channel blockade
alkalinization of arterial blood pH: inhibits binding of TCA to myocardial Na+ channel as drug is not ionised
benefit due to increased pH and increased sodium

45
Q

What is the standard of care for TCA poisoning?

A

sodium bicarbonate

46
Q

What is the treatment if dysrhythmias continue from TCA poisoning despite sodium bicarbonate?

A

lidocaine
-blocker of Na+ and K+ channels
hypertonic saline
magnesium sulfate

47
Q

Which drugs should not be given during dysrhythmias from TCAs?

A

class IA or IC antiarrhythmics
beta blockers
physostigmine and type 3 anti-dysrhythmic agents
flumazenil

48
Q

What is the management of seizures caused by TCA toxicity?

A

benzodiazepines
sodium bicarbonate may also help manage/prevent seizures if QRS complex is shortened

49
Q

What is the role of decontamination in TCA toxicity?

A

?/maybe gastric lavage
-reasonable in adults with intentional OD
-risk of aspiration
SDAC
-binds
-risk of aspiration

50
Q

What is the role of elimination in TCA toxicity?

A

maybe MDAC
no hemodialysis
-PPB, lipophilic, Vd

51
Q

What is the antidote for TCA toxicity?

A

intravenous lipid emulsion
-hemodynamically unstable patients or those in cardiac arrest unresponsive to conventional therapy
-also in patients where bicarbonate is not effective

PHAR324 (11 decks)

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