Tricyclic Overdose

Question 1

Name some tricyclic drugs:

Answer 1

• Amitriptyline
• Doxepin
• Dosulepin

Question 2

What is the mechanism of action in a tricyclic overdose?

Answer 2

• Serotonin-noradrenaline receptor inhibitor
• block transport of serotonin transporter and norepinephrine transportor
• results in elevation of synaptic concentration of neurotransmitters
• high dose =cardiovascular and neurotoxicity

Question 3

What are the early signs of tricyclic overdose?

Answer 3

Anticholinergic effects:

• Dry mouth
• Dilated pupils
• Agitation
• Sinus tachy
• Blurred vision

Due to norepinephrine receptors all over the body causes many physical signs

Question 4

What are the anticholinergic effects of tricyclic overdose?

Answer 4

• Altered mental state
• Dry mouth
• mydriasis= dilated pupils
• fever
• resting tachy
• urinary retention
• Constipation
• vomiting

Question 5

What are the features of sever tricyclic overdose poisoning?

Answer 5

• Arrhythmias
• seizures
• metabolic acidosis
• Coma

Question 6

What are the ECG changes in tricyclic overdose?

Answer 6

• Sinus tachy
• Widening of QRS
• prolongation of QT interval

Question 7

What is the management of Tricyclic ovedose?

Answer 7

1. A-E assessment
2. ECG, ABG, Serum TCA concentrations
3. Activation charcoal if presenting within 2hours
4. IV bicarbonate
   >2mmol/kg rapid bolus
   >first line for hypotension and arrhythmia
   >indications include widening of QRS >100ms or ventricular arrhythmia