QuestionSBA
QuestionChoice
This, or IV lorazepam, is a second line option after IV sodium bicarbonate
31870
c
Diazepam
QuestionChoice
This is used in the management of paracetamol overdose
31872
e
N-acetylcysteine
QuestionChoice
Sodium bicarbonate is indicated in patients with a tricyclic antidepressant (TCA) overdose who have an arrhythmia. This should be bolused, and once narrowing of the QRS is shown, this should be switched to an infusion
31868
a
Sodium bicarbonate
QuestionChoice
Vitamin K may be used to reverse warfarin ovedose
31869
b
Vitamin K
QuestionChoice
This is a tertiary option after IV sodium bicarbonate and IV benzodiazepine
31871
d
Phenobarbital
Concept
Chapter
# Summary

Tricyclic antidepressants (TCAs) e.g. amitriptyline, are primarily noradrenaline and serotonin reuptake inhibitors, which may be fatal in overdose. Key signs and symptoms include drowsiness, confusion, arrhythmias, seizures, vomiting, headache, dry mouth and dilated pupils. Investigations include a blood gas looking for acidosis, bloods for electrolyte disturbances (hypokalaemia may occur) and an ECG to check for arrhythmias. Management is supportive; activated charcoal can be given to patients presenting within an hour of the overdose and sodium bicarbonate is used to treat arrhythmias and acidosis. 
 
# Definition
 
Tricyclic antidepressants (TCAs) are a class of drugs that act as noradrenaline and serotonin reuptake inhibitors. Examples include amitriptyline, dosulepin and nortriptyline.

They are now less commonly prescribed than other antidepressant classes, but are often used for other indications such as neuropathic pain or migraine prophylaxis. 

TCA overdose can cause severe toxicity due to blockade of sodium channels and antimuscarinic effects. Neurological and cardiovascular toxicities predominate, although anticholinergic symptoms are wide-ranging.

# Aetiology

The majority of cases of TCA overdose are intentional as a means of self-harm or a suicide attempt. Accidental ingestion may also occur, particularly in children.

TCAs have a narrow therapeutic index and a dose of 10-20 mg/kg represents a potentially fatal overdose.
 
# Signs and Symptoms
 
Symptoms include:

- Palpitations
- Drowsiness
- Dry mouth
- Hot, dry skin
- Confusion
- Hallucinations
- Headache
- Nausea and vomiting

Signs include:

 - Reduced level of consciousness
 - Seizures
 - Mydriasis
 - Urinary retention
 - Ileus
 - Hypotension
 - Tachycardia
 

# Differential Diagnosis

- **Sodium channel blocker overdose** e.g. antiarrhythmics such as flecainide or quinine; cause similar ECG findings with arrhythmias and QRS widening as well as seizures and coma
- **Anticholinergic overdose** other medications such as carbamazepine, antipsychotics and antihistamines as well as plants (e.g. deadly nightshade) have similar manifestations in overdose with cardiovascular and neurological effects
- **Alcohol intoxication** can cause overlapping symptoms of nausea and vomiting, drowsiness and reduced levels of consciousness but not the anticholinergic effects

# Investigations

**Bedside tests:**

- **ECG** typically shows a widened QRS and prolonged QTc, may progress to life-threatening arrhythmias (QRS > 100ms is predictive of seizures; >160ms of ventricular arrhythmias)
- **Venous blood gas** looking for acidosis (usually mixed respiratory and metabolic)
- **Bladder scan** if urinary retention is suspected to confirm need for a catheter
- **Capillary blood glucose** to rule out hypoglycaemia as a cause of symptoms

**Blood tests:**

- **Full blood count** as a baseline
- **U&Es** looking for hypokalaemia that increases the risk of arrhythmias, and renal impairment that increases the risk of toxicity
- **Bone profile and magnesium** looking for other electrolyte abnormalities that may contribute to arrhythmias
- **LFTs** especially if concurrent paracetamol overdose is suspected
- **Paracetamol and salicylate levels** to screen for other concurrent overdoses
 
[lightgallery]
 
# Management
 
- A to E approach; ensure airway is secured if reduced level of consciousness or seizures
- **Cardiac monitoring** if significant overdose or ECG changes
- Give **activated charcoal** if within 1 hour of overdose (via an NG tube if needed)
- Resuscitate with **IV fluids** +/- vasopressors if hypotensive
- Give **IV sodium bicarbonate** if acidotic, QRS prolongation or arrhythmias 
- **Benzodiazepines** may be required for agitation or seizures
- **Intensive care admission** may be required in significant overdose - hyperventilation can be used in intubated patients to treat acidosis
- **Catheterise** if in urinary retention
- **Psychiatry input** once recovered for patients who have taken an intentional overdose

# NICE Guidelines

[NICE CKS - Antidepressant toxicity in overdose](https://cks.nice.org.uk/topics/depression/prescribing-information/antidepressant-toxicity-in-overdose/)

# References
 
[Life in the Fast Lane - Tricyclic Overdose](https://litfl.com/tricyclic-overdose-sodium-channel-blocker-toxicity/)

[Emergency Medical Minute - Tricyclic Overdose](https://emergencymedicalminute.org/tca-overdose/)
709
Picture
A prolonged QT seen on an ECG.
696
Long QT syndrome.png
images/pw1h45rr1665036171701.jpg
images/pw1h45rr1665036171701_256.jpg
images/pw1h45rr1665036171701_512.jpg
NggGBICHh3ePh4hweI9kpgClRQ==
2476
Tricyclic antidepressant overdose
Topic
39
Emergency Medicine
6374
Sodium bicarbonate is the treatment of choice for ventricular arrhythmias in tricyclic antidepressant overdose, particularly to narrow the QRS complex.
A patient self presents after taking an overdose of their amitriptyline approximately two and a half hours ago. An ECG shows a ventricular arrhythmia.

Which of the following is indicated in this patient?
a