# Tricyclic Antidepressant Toxicity

Manage suspected tricyclic antidepressant toxicity by immediate airway and hemodynamic stabilization, continuous ECG monitoring, and early sodium bicarbonate for QRS widening, acidosis, dysrhythmia, or shock. Serial ECG, pH, and electrolyte results guide alkalinization and ICU-level escalation.

**Clinical question:** How should clinicians identify, stabilize, alkalinize, monitor, and disposition patients with suspected tricyclic antidepressant toxicity?

Updated: 2026-09-16T00:11:22.006749+00:00

## What matters in practice
- Obtain an ECG immediately and use QRS duration, rather than a quantitative TCA concentration, to identify sodium-channel blockade requiring treatment; QRS greater than 100 ms is a treatment threshold for sodium bicarbonate. [2][3][21]
- Give sodium bicarbonate boluses for QRS greater than 100 ms and titrate toward QRS less than 100 ms while limiting serum pH to approximately 7.50-7.55. [2][3]
- Treat acidosis, hypoxia, electrolyte abnormalities, seizures, hypotension, and dysrhythmias concurrently because each can worsen cardiovascular toxicity. [2][10][12]
- Admit patients with hypotension, wide-complex tachycardia, seizures, coma, or significant anticholinergic toxicity to an ICU-capable setting; patients without ECG abnormalities, altered mental status, seizures, or hypotension during 6 hours are lower risk. [2][12]
- Avoid physostigmine in TCA toxicity because reported cases describe asystole after its administration. [13]

## Stabilize suspected TCA toxicity before confirmatory testing

Rapid deterioration can occur within 1-2 hours after ingestion. [4]

Perform immediate airway, breathing, and circulation assessment; establish IV access, apply continuous cardiac monitoring, and obtain a 12-lead ECG. Obtain serial ECGs when toxicity is evolving or severe. [2][3][22]

Treat hypoxia, acidemia, and electrolyte abnormalities promptly because cardiovascular complications are managed in part by correcting these reversible amplifiers of sodium-channel blockade. [2] In patients with depressed consciousness, seizures, shock, or unstable wide-complex tachycardia, manage in a resuscitation-capable setting while initiating serum alkalinization. [2][3]

For hypotension, begin isotonic crystalloid boluses. If shock persists, use an alpha-adrenergic vasopressor such as norepinephrine or phenylephrine; severe hypotension should not delay sodium bicarbonate when there is QRS widening or other evidence of cardiotoxicity. [11][12]
- Obtain a venous pH and electrolytes with serial ECG assessment in severe acute toxicity. [22]
- Obtain acetaminophen, salicylate, and ethanol concentrations when evaluating overdose; a TCA screen may be qualitative and does not replace ECG-directed management. [21]
- Use activated charcoal only as gastrointestinal decontamination intended to bind unabsorbed drug; prioritize stabilization first. [3]

*Immediate findings that change triage and treatment in suspected TCA toxicity. [2][3][12]*

| Finding | Interpretation | Immediate action |
| --- | --- | --- |
| QRS >100 ms | Clinically important sodium-channel blockade and increased complication risk. [2][12] | Give sodium bicarbonate boluses; target QRS <100 ms while keeping pH no higher than 7.55. [2][3] |
| pH <7.45 | Acidemia can worsen toxicity. [3] | Initiate sodium bicarbonate-directed alkalinization when accompanied by suspected TCA toxicity; reassess pH and ECG serially. [3][22] |
| SBP <90 mmHg | High-risk toxicity requiring aggressive hemodynamic management. [2] | Give isotonic crystalloid; add vasopressor support if needed and treat concurrent cardiotoxicity with sodium bicarbonate. [11][12] |
| Coma, seizure, or wide-complex tachycardia | Major toxicity and need for critical-care monitoring. [2][3] | Resuscitate, treat seizures with benzodiazepines when prolonged, obtain serial ECG/pH/electrolytes, and admit to ICU-capable care. [2][12][22] |

## Use the ECG to identify sodium-channel blockade and predict deterioration

The initial ECG is the pivotal bedside test.

In suspected TCA ingestion, obtain an ECG even when the history is incomplete. Typical progression includes sinus tachycardia followed by QRS widening, wide-complex tachycardia, and ventricular arrhythmias as toxicity becomes more severe. [4] QRS prolongation is a recognized predictor of subsequent complications, although coma may also identify high-risk patients. [2]

Treat a QRS duration greater than 100 ms as actionable cardiotoxicity. Sodium bicarbonate boluses are recommended to narrow the QRS to less than 100 ms, provided serum pH does not exceed 7.55. [2][3] Continue cardiac monitoring during treatment because recurrent clinical or ECG toxicity may require repeated bicarbonate therapy. [12]

Do not use a quantitative amitriptyline concentration to determine acute bedside risk when ECG findings are available. ACEP educational guidance notes that testing may provide only a qualitative TCA screen; management is directed by clinical toxicity, ECG changes, pH, and hemodynamics. [21][22]
- Repeat ECG every 1-2 hours in severe acute toxicity, together with venous pH and electrolytes. [22]
- Escalate monitoring rather than relying on a reassuring single ECG when ingestion is recent or symptoms are progressing during the early 1-2-hour deterioration window. [4][22]
- A patient without QRS widening, conduction abnormality, altered mental status, seizure, or hypotension during 6 hours is lower risk for severe toxicity. [12]

*ECG- and physiology-directed interpretation for TCA toxicity. [2][3][12][22]*

| Parameter | Actionable threshold or pattern | Management consequence |
| --- | --- | --- |
| QRS duration | >100 ms. [2][3][12] | Administer sodium bicarbonate boluses and titrate to QRS <100 ms. [2][3] |
| Serum pH | <7.45 with toxicity; avoid pH >7.55 during therapy. [3] | Correct acidemia; limit bicarbonate-driven alkalinization at pH 7.50-7.55. [3] |
| Serial ECG | Worsening QRS or recurrent conduction abnormality. [12][22] | Repeat bicarbonate treatment as clinical signs recur and continue monitored care. [12] |
| Six-hour observation | No ECG abnormality, altered mental status, seizure, or hypotension. [12] | Risk of severe toxicity is lower; ongoing disposition remains dependent on exposure circumstances and clinical assessment. [12] |

## Administer sodium bicarbonate for QRS widening and cardiovascular toxicity

Alkalinization and sodium loading address TCA-mediated cardiac sodium-channel blockade.

Give sodium bicarbonate boluses for QRS greater than 100 ms, aiming to narrow the QRS below 100 ms and maintain a maximum pH of 7.50-7.55. [2][3] Bicarbonate is also used when TCA poisoning is complicated by metabolic acidosis, malignant dysrhythmia, hypotension, or cardiac arrest. [10]

A practical ACEP simulation regimen uses 2-4 ampules of sodium bicarbonate as an initial bolus, followed by an infusion of 150 mEq sodium bicarbonate in 1 L D5W. [21] Reassess the QRS, venous pH, potassium, and other electrolytes after boluses and during infusion; serial ECG, pH, and electrolyte checks every 1-2 hours are recommended in severe acute toxicity. [22]

Avoid over-alkalinization. When further sodium loading is required but pH approaches the target ceiling, described alternatives include 3% sodium chloride without bicarbonate or modest permissive hypercapnia in a mechanically ventilated patient to permit additional bicarbonate boluses. These strategies require specialist-guided critical-care management. [3]
- Do not delay bicarbonate in a patient with wide QRS and shock while awaiting toxicology results. [2][3][21]
- Repeat sodium bicarbonate when ECG or clinical toxicity recurs, while maintaining continuous cardiac monitoring. [12]
- Consult a poison center or medical toxicologist for refractory cardiotoxicity, difficult alkalinization targets, or consideration of hypertonic saline after adequate bicarbonate-directed alkalinization and resuscitation have failed. [3][12]

### Safety limits and interaction-relevant considerations

Sodium bicarbonate injection labeling lists renal failure, respiratory or metabolic alkalosis, hypoventilation, hypernatremia, hypertension, edema, congestive heart failure, and persistent potassium depletion or hypocalcemia among contraindications or major cautions. In life-threatening TCA cardiotoxicity, balance these risks against the need to reverse sodium-channel blockade, using frequent pH, sodium, potassium, calcium, volume-status, and ECG reassessment. [1]
- Sodium bicarbonate can lower serum potassium, particularly with potassium-depleting diuretics; monitor and correct potassium during prolonged alkalinization. [1]
- Alkalinization increases renal clearance of acidic drugs, including salicylates and some barbiturates, and can prolong the half-life of basic drugs such as amphetamines and quinidine; consider coingestants when interpreting the clinical course. [1]

*Sodium bicarbonate treatment targets and escalation points. [2][3][21][22]*

| Treatment component | Supported approach | Monitoring or escalation |
| --- | --- | --- |
| Initial bolus | 2-4 ampules of sodium bicarbonate in ACEP simulation guidance. [21] | Repeat ECG and assess QRS response. [21][22] |
| Infusion | 150 mEq sodium bicarbonate in 1 L D5W after bolus in ACEP simulation guidance. [21] | Follow venous pH and electrolytes with serial ECGs. [22] |
| QRS target | Narrow QRS to <100 ms. [2][3] | Continue cardiac monitoring and repeat therapy if toxicity recurs. [12] |
| pH ceiling | Maximum pH 7.50-7.55. [2][3] | If more sodium loading is needed near this limit, obtain specialist guidance; 3% sodium chloride or permissive hypercapnia are described options. [3] |

## Treat seizures, arrhythmias, and shock while correcting the toxic milieu

Major arrhythmias usually occur with other severe toxic features. [3]

Treat prolonged seizures with benzodiazepines. [12] Do not administer flumazenil when benzodiazepines may have been coingested, because antagonism can unmask TCA-induced seizures. [12] Seizure, coma, hypotension, and wide-complex tachycardia should each trigger ICU-capable admission and ongoing ECG-directed alkalinization. [2][3]

For ventricular dysrhythmia or wide-complex tachycardia in TCA toxicity, first correct acidemia, hypoxia, electrolyte derangements, and sodium-channel blockade with sodium bicarbonate. [2][3] If major arrhythmia persists despite bicarbonate, management may require antiarrhythmic therapy in addition to bicarbonate under specialist direction. [3]

Do not use intravenous lipid emulsion as a substitute for sodium bicarbonate in hypotensive TCA toxicity: American Heart Association material reports no improvement in hypotension compared with sodium bicarbonate. [8] Hypertonic saline is a rescue option only after hypotension fails to respond to adequate bicarbonate alkalinization and aggressive fluid resuscitation. [12]
- Avoid physostigmine for TCA-associated anticholinergic manifestations; asystole after physostigmine has been reported in TCA overdose. [13]
- Use supportive management for anticholinergic manifestations rather than physostigmine. [12][13]
- For cardiac arrest caused by TCA poisoning, administer sodium bicarbonate as part of treatment for sodium-channel blockade and acidosis. [10]

*Complication-specific actions in severe TCA toxicity. [2][3][8][12][13]*

| Complication | First action | Avoid or escalate |
| --- | --- | --- |
| Prolonged seizure | Benzodiazepine treatment. [12] | Avoid flumazenil if benzodiazepine coingestion is possible. [12] |
| Wide-complex tachycardia or ventricular arrhythmia | Correct acidosis, hypoxia, electrolytes, and give sodium bicarbonate for QRS-directed alkalinization. [2][3] | Persistent major arrhythmia may require bicarbonate plus specialist-guided antiarrhythmic therapy. [3] |
| Hypotension | Isotonic crystalloid boluses, then norepinephrine or phenylephrine if needed. [11][12] | Consider hypertonic saline only after inadequate response to alkalinization and aggressive fluids. [12] |
| Anticholinergic findings | Supportive management. [12] | Avoid physostigmine because asystole has been reported. [13] |

## Use six-hour clinical and ECG observation to identify lower-risk patients

Disposition depends on observed toxicity, not reported dose alone.

Patients with hypotension, wide-complex tachycardia, coma, seizures, or significant anticholinergic toxicity require ICU-level admission after initial stabilization. [2][3] Continue continuous cardiac monitoring and obtain serial ECGs, venous pH, and electrolytes every 1-2 hours in severe acute toxicity. [22]

Severe toxicity generally occurs early. Patients who remain free of QRS widening, other conduction abnormalities, altered mental status, seizures, and hypotension during the first 6 hours can be classified as lower risk and no longer require PICU monitoring in the pediatric source; for accidental ingestion of a dose unlikely to be toxic, asymptomatic patients at 6 hours may be monitored at home per out-of-hospital guidance. [2][12] Intentional exposure, uncertain timing, coingestion, or unreliable observation should still drive a more conservative disposition decision.

Before stepping down monitoring after bicarbonate therapy, document sustained QRS normalization, hemodynamic stability, resolution of seizures or altered mental status, and a pH that is not above the recommended 7.50-7.55 ceiling. [2][3][22]
- Continue intensive monitoring when QRS widening recurs, because repeated bicarbonate therapy may be required. [12]
- Use ECG findings and clinical course rather than a qualitative TCA screen to determine ongoing monitoring intensity. [21][22]
- Arrange appropriate psychiatric assessment after medical stabilization for intentional ingestion.

*Monitoring and disposition framework for TCA toxicity. [2][12][22]*

| Clinical state | Monitoring location | Reassessment rule |
| --- | --- | --- |
| Shock, seizure, coma, wide-complex tachycardia, or marked anticholinergic toxicity | ICU-capable monitored setting. [2][3] | Serial ECG, venous pH, and electrolytes every 1-2 hours in severe acute toxicity. [22] |
| Persistent QRS widening or recurrent toxicity after treatment | Continuous cardiac monitoring. [12] | Repeat bicarbonate-directed treatment as clinical signs recur while limiting pH to 7.50-7.55. [2][3][12] |
| No ECG abnormality, altered mental status, seizure, or hypotension by 6 hours | Lower-risk group. [12] | Disposition depends on accidental versus intentional exposure, timing certainty, coingestions, and reliable observation. [2][12] |

## References
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## Editorial note

Prepared from cited clinical literature using Astra's research workflow. Verify recommendations against current guidance and patient-specific factors.