Tricyclic antidepressants such as amitriptyline are among the most dangerous drugs in overdose because they block sodium channels in the heart and have strong anticholinergic effects. A patient found after an unknown overdose can look stable at first and then quickly develop seizures, arrhythmias and low blood pressure.
Key symptoms
- Drowsiness or confusion that can progress to coma
- Agitation, hallucinations or slurred speech
- Dry mouth, flushed skin and trouble passing urine
- Palpitations and a fast heartbeat
- Seizures, often within hours of the ingestion
What you find on exam
- Airway, breathing and level of consciousness (GCS)
- Fast heart rate and low blood pressure
- Dilated pupils, dry hot skin and quiet bowel sounds
- Pill bottles, empty packets and other clues at the scene
- Repeated neuro checks; mental status can drop quickly
Tests
- 12-lead ECG: QRS wider than 100 ms and a tall terminal R wave in aVR
- Continuous cardiac monitoring
- Blood glucose, electrolytes and blood gas for acidosis
- Acetaminophen, salicylate and alcohol levels; urine drug screens add little
Treatment basics
- ABCs, oxygen, IV access and early transport to hospital
- Sodium bicarbonate IV bolus for a wide QRS, arrhythmias or low blood pressure
- Benzodiazepines such as midazolam or lorazepam for seizures
- IV fluids, then norepinephrine if blood pressure stays low
- Intubation for coma or airway risk; avoid flumazenil and physostigmine
Red flags
- QRS over 100 ms or a ventricular arrhythmia
- Seizure or rapidly falling consciousness
- Low blood pressure that does not improve with fluids
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Related guides
Sources: NASEMSO National Model EMS Clinical Guidelines; National EMS Education Standards (2021); NREMT psychomotor skill sheets (EMT and Paramedic). Written by Making Synapses. Making Synapses is not affiliated with these organizations.