Makindo Medical Notes

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Calcium channel blocker toxicity represents a serious, potentially fatal overdose situation—prompt action is essential.

About

• Calcium channel blocker toxicity involves the overdose of medications that block calcium channels in the heart and blood vessels.
• Overdose can be life-threatening and requires immediate medical attention.
• Act quickly and seek expert advice to manage the condition effectively.

Aetiology

• Amlodipine, Felodipine, and Nifedipine primarily act as peripheral vasodilators, which can lead to significant hypotension.
• Verapamil and Diltiazem exert effects on the heart, causing bradycardia and reduced myocardial contractility due to their negative inotropic effects.
• Verapamil specifically inhibits calcium influx in myocardial and vascular tissues through L-type calcium channels, exacerbating cardiac depression during overdose.

Clinical Features

• Severe bradycardia and/or hypotension are hallmark signs of toxicity.
• Symptoms may include syncope, presyncope, collapse, and potentially asystole.
• Patients may present with altered mental status and signs of shock.

Investigations

• Laboratory Tests: Complete Blood Count (CBC), Urea & Electrolytes (U&E), Magnesium (Mg), and Calcium (Ca).
• ECG: Continuous monitoring for bradycardia, conduction delays, and other arrhythmias.
• Troponin: Measure if acute coronary syndrome is suspected, particularly in cases with chest pain.

Management

• Continuous Monitoring: ECG monitoring should occur in a Coronary Care Unit (CCU), Intensive Therapy Unit (ITU), or High Dependency Unit (HDU) for at least 12 hours, especially with extended-release formulations.
• Hypotension: Administer IV crystalloids for volume support; titrate according to blood pressure response.
• Bradycardia: Administer IV Atropine at doses of 0.6–1.2 mg as needed; repeated doses may be required.
• Calcium Gluconate: Administer 10–20 mL of a 10% solution slowly via IV; may repeat or administer as an infusion, aiming for mild hypercalcemia to improve cardiac contractility.
• Decontamination: Consider whole-bowel irrigation with polyethylene glycol and activated charcoal, particularly in cases of sustained-release verapamil overdose.
• Hyperinsulinaemic Euglycaemic (HIE) Therapy: Initiate high-dose insulin infusion (up to 1.0 U/kg per hour) along with IV dextrose to prevent hypoglycemia; closely monitor blood glucose and potassium levels.
• Glucagon: Consider glucagon administration if hypotension persists after other interventions; it may enhance cardiac contractility.
• Lipid Emulsion Therapy: In severe cases, this therapy may be beneficial, with anecdotal evidence supporting its use in lipid-soluble drug toxicity.
• High-dose Dopamine: Can be used to counteract systemic vasodilation and improve perfusion in hypotensive patients.
• Cardiac Pacing: Temporary pacing may be necessary if significant bradycardia persists despite treatment.

References

• Hyperinsulinaemic Euglycaemia Therapy for Verapamil Poisoning: A Review