Toxicology 8.8 E) Ii) Tricyclic Antidepressants

Front 1

Which is incorrect regarding TCA overdose?
1. Ingestion of > 10mg/kg is potentially life threatening
2. Onset of severe toxicity is usually within 2 hours of ingestion
3. Myocardial toxicity is due to blockade of activated fast sodium

channels
4. TCA's have noradrenaline and serotonin reuptake inhibition
5. TCA's block muscarinic {M1} , Histamine {H1} and peripheral

post-synaptic alpha 1 adrenergic receptors.

Back 1

3. blockade of INACTIVATED fast sodium

channels

Front 2

What 3 main systems are effected by TCA

overdose?

Back 2

1. CNS
2. CVS
3. Autonomic - Anticholinergic

Front 3

Which is incorrect regarding the Clinical

features of TCA overdose?
1. Sedation and coma usually precede cardiovascular signs
2. Delerium occurs secondary to anticholinergic effects
3. Hypotension is due to alpha blocking effects PLUS myocardial

depression.
4. Anticholinergic effects include ileus, myoclonic jerks and miosis
5. Warm, dry skin is likely, not diaphoresis.

Back 3

4. mydriasis

Front 4

Diagnostic features of TCA overdose on ECG?

Back 4

1. Prolongation:
a. PR interval
b. QRS
c. QT interval [ K+ channel blockade]
2. aVR:
a. large terminal R wave
b. Increased R/S ratio [ > 0.7 ]

Front 5

QRS widening in TCA overdose:

a. Widening reflects degree of ?
b. QRS > 100ms predicts ?
c. QRS > 160ms predicts ?

Back 5

a. Fast sodium channel blockade
b. Seizures
c. Ventricular tachycardia

Front 6

Which is incorrect regarding ventricular

arrhythmias and TCA overdose?
1. Cardioversion and defibrillation is unlikely to be effective
2. Sodium bicarbonate is given until "restoration of perfusing rhythm" and pH >7.5
3. Adrenaline and noradrenaline infusions can be used for hypotension unresponsive to crystalloid

4. Intubated patients are hyperventilated to maintain pH 7.45-7.55

Back 6

4. pH > 7.50-7.55

Front 7

In regards to TCA overdose , which is incorrect?
1. Activated charcoal is not indicated for ingestions < 10mg/kg

2. GCS < 13 = intubation
3. Lignocaine can be given - 1.5 mg/kg IV after pH > 7.5
4. B blockers and amiodarone are contraindicated

Back 7

2. GCS < 12

Front 8

List the ECG effects in TCA overdose

Back 8

1. Prolongation
- PR
- QRS
- QT
2. R axis deviation
3. Large R wave in aVR

**** The most common ECG finding is sinus tachycardia ***
Other
4. AV block
5. Ventricular ectopy
6. Non-specific ST-T wave changes
7. Brugada pattern [ RBBB + downsloping ST segment elevation in V1-V3]

Front 9

Which of the following is not considered one of the main fast sodium channel blockers in

Toxicology?
A. Bupivicaine
B. Diphenhydramine
C. Bretylium
D. Propoxyphene.

Back 9

C.

Front 10

Which of the following is not considered one of the main sodium channel blockers of concern in Toxicology?

A. Quinine
B. Valproate
C. Cocaine
D. Hydroxychloroquine

Back 10

B.

Front 11

Which of the following is not considered one of the main sodium channel blockers of concern in Toxicology?

A. Carbamazepine
B. Thioridazine
C. Olanzapine
D. Amantadine

Back 11

C. ( Blocks potassium efflux = QT prolongation)