Poisoning approach and drug overdoses

Cardiotoxic overdoses: TCA, beta-blockers, CCB, digoxin

Reviewed Nov 2026·5 references
New· views rounded down, updated weekly

Sodium bicarbonate for sodium-channel blockade, calcium and high-dose insulin for CCB/beta-blocker shock, digoxin Fab, lipid and ECMO as rescue.

Definition
Drugs causing shock and arrhythmia: sodium-channel blockers (TCA, flecainide, carbamazepine) widen QRS; CCBs (especially amlodipine, verapamil, diltiazem) and beta-blockers cause bradycardia, vasodilation and myocardial depression; digoxin causes arrhythmias and hyperkalaemia.

At the bedside

  1. 1

    TCA / sodium-channel blockade

    QRS > 100 ms, R in aVR > 3 mm, arrhythmia or hypotension: sodium bicarbonate 1-2 mEq/kg bolus, repeat to narrow QRS; keep pH 7.45-7.55; hyperventilate if intubated. Benzodiazepines for seizures.

  2. 2

    CCB poisoning (consensus 2017)

    First line: IV calcium, high-dose insulin (with dextrose), vasopressors/inotropes (noradrenaline or adrenaline), atropine for symptomatic bradycardia. Decontaminate (WBI for sustained-release).

  3. 3

    Refractory CCB

    Increase insulin up to 10 units/kg/h, pacing for bradycardia, lipid emulsion in peri-arrest, VA-ECMO for cardiogenic shock in centres where available.

  4. 4

    Beta-blocker poisoning

    Atropine, glucagon (bolus then infusion), high-dose insulin, adrenaline/noradrenaline; propranolol behaves like a sodium-channel blocker (bicarbonate for wide QRS).

  5. 5

    Digoxin

    Fab for life-threatening arrhythmia, K > 6 mmol/L in acute toxicity, or end-organ hypoperfusion. Treat hyperkalaemia with insulin-dextrose; avoid electrical pacing if possible.

  6. 6

    Monitor

    Continuous ECG, arterial line, glucose every 15-30 min on HIET, K hourly, echocardiography to distinguish vasoplegia from pump failure.

TCA with QRS > 100 ms

Sodium bicarbonate 8.4%

IV
Dose
1-2 mEq/kg bolus, repeat to QRS < 100 ms
Target
pH 7.45-7.55, Na < 155 mmol/L
Worked example
70 kg: 70-140 mL of 8.4% over 2-5 min

CCB toxicity

Calcium chloride 10% / gluconate 10%

IV (central)
Dose
10% chloride 10-20 mL (or gluconate 30-60 mL), repeat every 10-20 min
Worked example
70 kg: 20 mL 10% CaCl2 over 5-10 min; infusion 14-28 mL/h

CCB / beta-blocker shock

Insulin (high-dose insulin euglycaemic therapy)

IV
Dose
1 units/kg bolus, then 1 units/kg/h up to 10 units/kg/h
Preparation
500 units in 50 mL NS = 10 units/mL
Worked example
70 kg: 70 units bolus; infusion 70 units/h = 7 mL/h; dextrose 35 g/h (e.g. 25% dextrose 140 mL/h via central line)
Open infusion calculator

Beta-blocker toxicity

Glucagon

IV
Dose
5 mg bolus (repeat to 10 mg), then 3-5 mg/h

Peri-arrest lipophilic drug toxicity

Lipid emulsion 20%

IV
Dose
1.5 mL/kg bolus, then 0.25 mL/kg/min
Worked example
70 kg: 100 mL bolus, then 17.5 mL/min for 30-60 min

Digoxin toxicity

Digoxin-specific antibody fragments (Fab)

IV
Dose
Acute: 2-5 vials titrated; chronic 1-2 vials
Red flag · call your senior now
Amlodipine overdose can cause delayed (12-24 h) severe vasoplegia and non-cardiogenic pulmonary oedema; monitor in ICU for at least 24 h.
Pitfall
Stopping high-dose insulin because glucose falls: give more dextrose instead.
Pitfall
Class IA/IC antiarrhythmics or physostigmine in TCA toxicity.
Pearl
Use echo: CCB shock with good contractility needs vasopressors; poor contractility needs insulin/inotropes.

Calculators for this topic

Infusion rate from per-kg-per-hour dose

Pump rate for drugs dosed per kg per hour (insulin U/kg/h, midazolam mg/kg/h, propofol mg/kg/h, fentanyl mcg/kg/h, dexmedetomidine mcg/kg/h).

Corrected QT (Bazett)

QT ÷ √(RR in seconds). Over-corrects at fast heart rates.

References

  1. 1

    St-Onge M, Anseeuw K, Cantrell FL, et al. Experts consensus recommendations for the management of calcium channel blocker poisoning in adults. Crit Care Med 2017;45:e306-15.

  2. 2

    Engebretsen KM, Kaczmarek KM, Morgan J, Holger JS. High-dose insulin therapy in beta-blocker and calcium channel-blocker poisoning. Clin Toxicol 2011;49:277-83.

  3. 3

    Gosselin S, Hoegberg LCG, Hoffman RS, et al. Evidence-based recommendations on the use of intravenous lipid emulsion therapy in poisoning. Clin Toxicol 2016;54:899-923.

  4. 4

    Chan BS, Buckley NA. Digoxin-specific antibody fragments in the treatment of digoxin toxicity. Clin Toxicol 2014;52:824-36.

  5. 5

    Farkas J. The Internet Book of Critical Care (IBCC). EMCrit Project; continuously updated.

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