Related Subjects:
|Drug Toxicity - Assessment
|Metabolic acidosis
|Aspirin or Salicylates toxicity
|Ethylene glycol toxicity
|Ethanol toxicity
|Methanol toxicity
|Ricin toxicity
|Carbon Tetrachloride Toxicity
|Renal Tubular Acidosis
|Lactic acidosis
|Iron Toxicity
|Tricyclic Antidepressant Toxicity
|Opiate Toxicity
|Carbon monoxide Toxicity
|Benzodiazepine Toxicity
|Paracetamol (Acetaminophen) toxicity
|Amphetamine toxicity
|Beta Blocker toxicity
|Calcium channel blockers toxicity
|Cannabis toxicity
|Cyanide toxicity
|Digoxin Toxicity
|Lithium Toxicity
|NSAIDS Toxicity
|Ecstasy toxicity
|Paraquat toxicity
|Quinine toxicity
|SSRI Toxicity
|Theophylline Toxicity
|LSD Toxicity
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|Toxin elimination by dialysis
|Drug Toxicity with Specific Antidotes
⚠️ Tricyclic Antidepressant (TCA) Toxicity is a potentially life-threatening condition following overdose of drugs such as amitriptyline, nortriptyline, imipramine, and doxepin.
📈 A QRS >100 ms on ECG = ↑ risk of seizures & arrhythmias.
⏱ ECG monitoring for at least 6 hrs is essential.
💉 IV Sodium Bicarbonate can narrow QRS and stabilise the myocardium (plasma alkalinisation).
| 🚨 Moderate/Severe TCA Toxicity – Key Steps |
|---|
- 🫁 ABC – Oxygen if hypoxic; IV fluids for hypotension; admit CCU/ITU.
- 💊 Activated Charcoal if within 1–2 hrs of ingestion (if alert/airway protected).
- 📉 QRS >100 ms → ↑ seizure/arrhythmia risk.
- 💉 IV Sodium Bicarbonate (1–2 mmol/kg bolus) → narrows QRS & ↑ BP.
- ⚡ Lidocaine for VT; Magnesium Sulfate for torsades de pointes.
- 💤 IV Lorazepam 2–4 mg for seizures. ❌ Avoid Phenytoin (cardiotoxic).
|
📌 About
- Toxicity results from multiple receptor actions.
- Even with hospital arrival, mortality risk remains high.
- Common agents: amitriptyline, imipramine, dothiepin.
🧬 Pharmacology (Mechanisms of Toxicity)
- ⬆️ Anticholinergic effects (dry mouth, urinary retention, delirium).
- ⬇️ Alpha-adrenergic blockade (→ hypotension).
- Inhibit NA & 5-HT reuptake.
- Block fast Na⁺ channels → widened QRS & arrhythmias ❤️.
- Block HERG K⁺ channels → prolonged QT.
- Histamine receptor blockade → sedation 🛌.
🩺 Clinical Features
- Drowsiness, ↓ GCS → coma risk.
- 👁 Dilated pupils; 🤯 seizures; 🤢 urinary retention.
- Hypotension & arrhythmias (life-threatening) ❤️.
- Neurological: ataxia, nystagmus, hyperreflexia, ↑ tone.
- Respiratory depression with coma; hyperthermia possible.
🔬 Investigations
- Bloods: FBC, U&E, LFTs, lactate.
- ABG: monitor pH (target 7.45–7.55 if alkalinising).
- ECG: prolonged PR, QRS, QT; AV block; non-specific ST/T changes.
- CXR: if aspiration suspected.
- CT head: if unexplained coma.
- Always check paracetamol & aspirin levels (common co-ingestion).
💉 Management
- 🔴 ABC resus, O₂, IV fluids; CCU/ITU monitoring.
- 🕒 Activated Charcoal if within 1–2 hrs (>10 tablets ingested).
- 📈 Cardiac monitoring for 6–12 hrs; QRS >140 ms → very high risk.
- 💉 Sodium Bicarbonate bolus/infusion → aim pH 7.45–7.55 (↑ binding, ↓ arrhythmia risk, ↑ BP).
- ⚡ Ventricular arrhythmias: overdrive pacing, MgSO₄, Lidocaine (not class 1a/1c agents).
- ❌ Haemodialysis not effective (high protein binding).
- 📉 If stable after 24 hrs → complications less likely.
📚 References
