Tricyclic antidepressants are all toxic in overdose but the most toxic are dothiepin and amitriptyline.
Features of tricyclic overdose:
- Anticholinergic
- blurred vision
- dilated pupils
- dry mouth
- tachycardia
- urinary retention
- pyrexia
- constipation
- Alpha adrenergic blockade
- hypotension
- Sodium channel blockade
- prolongation of QRS, PR and QT leading to risk of arrhythmias
Investigations
- UEs – look for hypokalaemia
- ABG –look for acidosis, classically mixed metabolic and respiratory
- ECG - ?long PR/long QT/broad QRS
Management
- ECG monitoring and observation
- Activated charcoal if patient presents within 1 hour and has an intact airway
- Gastric lavage if potentially life-threatening OD and within 1 hour of ingestion
- IV fluids if hypotensive
- Sodium bicarbonate if acidotic or arrthymias or hypotensive
- Avoid class Ia/Ic/III antiarrythmics as they prolong QT
- Use benzodiazepines to control seizures; avoid phenytoin
- Potentially ITU
Small print gem: Even if mixed OD with benzodiazepines avoid flumazenil as this increases risk of seizures and arrhythmias
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