Tricyclic Antidepressants Overdose

Question 1

Which two tricyclic antidepressants are especially dangerous in overdose?

Answer 1

Amitriptyline and dosulepin (dothiepin) are particularly dangerous in overdose

Question 2

What are the early features of tricyclic overdose?

Answer 2

Anticholinergic properties:

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

Question 3

What are the features of severe tricyclic poisoning?

Answer 3

Features of severe poisoning include:

• arrhythmias
• seizures
• metabolic acidosis
• coma

ECG changes include:

• sinus tachycardia
• widening of QRS
• prolongation of QT interval

Widening of QRS > 100ms is associated with an increased risk of seizures whilst QRS > 160ms is associated with ventricular arrhythmias

Question 4

How is tricyclic overdose treated?

Answer 4

IV bicarbonate used for hypotension or arrhythmias

Avoid drugs that prolong depolarisation or QTi (e.g. quinidine, flecanide, amiodarone)

IV lipid emulsion to bind free drug and reduce toxicity

Remember, dialysis is ineffective in removing tricyclics

Question 5

What ECG charges are associated with tricyclic overdose?

Answer 5

Sinus tachycardia

Widening QRS

Prolonged QT (normal <440 ms)