Calcium Channel Blocker Overdose Management

BACKGROUND

Calcium channel blockers (CCB) are used to in the treatment of angina, hypertension, and the rate control of tachyarrhythmias. The most commonly prescribed agents are verapamil, diltiazem, amlodipine, and nifedipine; with immediate and modified release preparations available.

Common complications associated with overdose of these agents includes hypotension and bradycardia whilst hyperglycaemia, hyperkalaemia, acidosis, ischaemic bowel and seizures may be encountered.

Death secondary to refractory hypotension, and cardiac suppression may develop up to 12 hours in immediate release preparations, and within 24 hours for modified release agents.

MANAGEMENT

Please refer to TOXBASE for definitive recommendations, however as a quick reference:

1. Gastric decontamination a. For patients presenting within 1 hour, particularly for modified release preparations, gastric lavage (in those with skills to do so), and/or activated charcoal

b. Multi-dose activated charcoal for late presentations of modified release agents

c. Consider whole-bowel irrigation with modified release agents

2. Bradycardia a. Treat with IV atropine (titrate to response)

b. Consider IV dobutamine, isoprenaline

c. Temporary pacing

3. Hypotension a. IV fluid bolus of 0.9% NaCl 20 mls/kg

b. IV calcium chloride or IV calcium gluconate as a slow bolus

c. IV Insulin & dextrose therapy as second-line agent

d. For treatment resistant cases, Intralipid may prove of benefit if the above measures fail

e. Consider IV inotropes, and/or mechanical means of blood pressure support

4. Cardiac Arrest a. For in-hospital, or witnessed cardiac arrest with immediate CPR, resuscitation should be continued for at least 1 hour.

NOTES

IV calcium therapy is used to temporarily restore blood pressure

Repeat doses (maximum 4), or an infusion may be required.

IV insulin & dextrose therapy (High Dose Insulin Euglycaemic Therapy, HIET) has been used successfully to restore cardiac function, and reverse hypotension in beta-blocker and CCB overdose, and is considered superior to inotropes for treatment resistant cases. HIET may be administered peripherally, reducing the time necessary to initiate treatment, but it may be up to 15 minutes for clinical effect to become apparent.