Tricyclic antidepressant overdose

Overview of tricyclic antidepressant overdose

Tricyclic antidepressant overdose occurs when a person takes more than the normal or recommended amount of a tricyclic antidepressant (TCA). This can happen by accident or on purpose. Overdose of TCAs is a medical emergency and can be life-threatening.

Signs and symptoms

Symptoms of TCA overdose can vary depending on the amount ingested and the time since ingestion. Common symptoms include:

• Central nervous system effects such as confusion, agitation, hallucinations, and seizures.
• Cardiovascular effects including tachycardia, hypotension, and arrhythmias.
• Anticholinergic effects such as dry mouth, dilated pupils, urinary retention, and hyperthermia.

Severe cases can lead to coma, respiratory depression, and cardiac arrest.

Pathophysiology

Tricyclic antidepressants work by inhibiting the reuptake of neurotransmitters such as serotonin and norepinephrine. In overdose, TCAs can block sodium channels in the heart, leading to QRS widening and potentially fatal arrhythmias. They also have anticholinergic properties, which contribute to many of the symptoms seen in overdose.

Diagnosis

Diagnosis of TCA overdose is primarily clinical, based on history and physical examination. An electrocardiogram (ECG) is crucial for identifying cardiac abnormalities such as QRS widening. Blood tests may be conducted to assess drug levels, although they are not always available or necessary for diagnosis.

Chemical structure of amitriptyline, a common tricyclic antidepressant.

ECG showing QRS widening in a patient with TCA overdose.

Treatment

Immediate treatment of TCA overdose involves stabilization of the patient's airway, breathing, and circulation. Activated charcoal may be administered if the patient presents within a few hours of ingestion. Sodium bicarbonate is the mainstay of treatment for cardiac toxicity, particularly for QRS widening and arrhythmias. Benzodiazepines may be used to control seizures.

Prognosis

The prognosis of TCA overdose depends on the amount ingested and the timeliness of treatment. With prompt medical intervention, many patients recover fully. However, severe cases can result in significant morbidity or mortality.

Prevention

Preventive measures include careful prescription practices, patient education on the risks of overdose, and monitoring of patients with a history of suicidal ideation.

Related pages

• Tricyclic antidepressant
• Antidepressant
• Overdose

Tricyclic antidepressant overdose

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  Electrocardiogram showing QRS widening in patient with TCA overdose