Antidepressant/Lithium/BZD Toxicity

Question 1

TCA is not really used for depression anymore. Why?

Answer 1

Due to high risk of toxicity, and safer alternatives

Question 2

T or F: Srs TCA toxicity can appear to be trivial.

Answer 2

T (which is why TCA’s are particularly dangerous)

Question 3

How well are TCAs absorbed?

Answer 3

Well absorbed

Question 4

TCA tmax?

Answer 4

up to 12h (OD dosing)

Question 5

What kind of effect do TCAs have on gastric emptying?

Answer 5

Delays it due to anticholinergic effects

Question 6

How extensive is plasma protein binding of TCAs?

Answer 6

V. extensive 85-98%

Question 7

TCAs are…

1. lipophilic
2. hydrophilic
3. amphipathic

Answer 7

1. lipophilic (highly)

Question 8

normal t1/2 of TCA? t1/2 in toxicity?

Answer 8

6-24h (up to 72h in toxicity)

Question 9

Why is TCA toxicity variable in the pop?

Answer 9

bc it’s metabolized by enzymes that are subject to genetic polymorphisms

Question 10

What is the main enzyme that metabolizes TCA?

Answer 10

2D6

Question 11

T or F: If the pt ingested a little TCA, then no need to worry too much

Answer 11

F

Dose ingested is a poor predictor of outcome

Question 12

CV signs/sx’s of TCA tox

Answer 12

Hypotn, cardiac dysrhythmias

Question 13

How do TCAs cause hypotn?

Answer 13

by antagonizing peripheral alpha-1 receptors on blood vessels

by causing dysrhythmias

by directly suppressing myocardial activity (binds Na channels)

Question 14

What’s important to do early on during TCA tox?

Answer 14

Take early ECG track heart’s electrical activity

Question 15

CNS signs/sx’s of TCA overdose?

Answer 15

agitation
seizures
coma (can be rapid)

Question 16

T or F: serum TCA levels are essential for TCA overdose dx

Answer 16

F

Question 17

Single most important diagnostic tool during TCA overdose

Answer 17

ECG

Question 18

TCA overdose: what does a QRS < 100ms tell us?

Answer 18

no seizure or ventricular arrhythmia

Question 19

TCA overdose: what does a QRS > 100ms tell us?

Answer 19

26% risk of seizure

Question 20

TCA overdose: what does a QRS > 160 ms tell us?

Answer 20

50% risk of ventricular arrhythmia

Question 21

What’s used to tx the hypotn assoc w/ TCA tox?

Answer 21

fluid boluses

Question 22

What’s used to tx dysrhythmias assoc w/ TCA tox?

Answer 22

NaHCO3

Question 23

How does NaHCO3 help with dysrhythmias?

Answer 23

The Na helps overcome the Na channel blockade induced by TCAs

AND

blood alkalinization > reducing TCA binding to myocardial Na channels

Question 24

T or F: NaHCO3 is used to enhance elimination of TCA faster from the body, much like it enhances elimination of salicylates

Answer 24

F

-NaHCO3 does NOT enhance elimination of the TCAs > we’re just treating sx’s and hoping for elimination of toxicity (this is unlike salicylates, which IS eliminated faster with NaHCO3)

Question 25

When would we give lidocaine to a pt suffering from TCA-induced ventricular fib or ventricular tachycardia?

Answer 25

If they're unresponsive to NaHCO3

Question 26

If NaHCO3 isn't helping w/ dysrhythmias assoc w/ TCA tox, what can we use?

Answer 26

lidocaine, hypertonic saline, magnesium sulfate

Question 27

What do we AVOID in TCA-induced dysrhythmias?

Answer 27

BBs, class IA and IC antiarrhytmics (may worsen cardiac depression/hypotn)

Question 28

What can we give for additional hypotn management during TCA toxicity (if NaHCO3 isn't enough)?

Answer 28

Vasopressors (NE is the best one), DA (not as effective)

Question 29

During TCA tox, what would make a pt's hypotn worse?

Answer 29

B-agonists (B2, specifically)

Question 30

During TCA tox, if a seizure arises, what should we give?

Answer 30

BZDs (diazepam)

Question 31

What is recommended for decontamination of TCAs?

Answer 31

Single dose activated charcoal

Question 32

Gastric lavage for TCA tox is reasonable in a certain situation.

Answer 32

Adults w/ intentional ODs

Question 33

Is hemodialysis useful for TCA tox? Why?

Answer 33

No > TCAs have extensive plasma protein binding, are lipophilic, and hence also distribute widely in tissues

Question 34

Antidote for TCA?

Answer 34

IV lipid emulsion (don't use if not life-threatening) -Based on case reports only

Question 35

What must be tx'ed right away during an MAOI-induced toxicity?

Answer 35

Hyperthermia

Question 36

Decontamination strats for MAOI-induced toxicity

Answer 36

SDAC, gastric lavage

Question 37

Elimination strats MAOI-induced toxicity

Answer 37

?MDAC | hemodialysis = not effective