Calcium Channel Blocker Overdose

Key Features

• All calcium channel blockers can cause arteriolar vasodilation and depression of cardiac contractility after acute overdose

• Examples of calcium channel blockers

  • Verapamil

  • Diltiazem

  • Nifedipine

  • Nicardipine

  • Amlodipine

  • Felodipine

  • Isradipine

  • Nisoldipine

  • Nimodipine

Clinical Findings

• Bradycardia, atrioventricular (AV) nodal block, hypotension, or a combination

• With severe poisoning, cardiac arrest may occur

Diagnosis

• Clinical

• Junctional bradycardia is common, with even moderate verapamil or diltiazem poisoning

Treatment

• Activated charcoal

  • Give 60–100 g mixed in aqueous slurry orally or via gastric tube

  • Do not use for comatose or convulsing patients unless they are endotracheally intubated

• Perform whole-bowel irrigation as soon as possible if a sustained-release product has been ingested

• Treat hypotension and bradycardia with calcium chloride intravenously

  • Start with 10%, 10 mL, or calcium gluconate, 20 mL; repeat the dose every 3–5 minutes

  • Maximum dose has not been established

  • Many toxicologists recommend raising the ionized serum calcium level to as much as twice the normal level

  • Calcium is most useful in reversing negative inotropic effects

  • It is less effective for AV nodal blockade and bradycardia

• High doses of insulin 0.5–1.0 units/kg bolus followed by 0.5–1.0 units/kg/h infusion with sufficient dextrose to maintain euglycemia may be beneficial

• Infusion of Intralipid 20% lipid emulsion has been reported to improve hemodynamics in animal models and case reports of calcium channel poisoning

• Methylene blue (1–2 mg/kg) was reported to reverse refractory shock due to profound vasodilation in a patient with amlodipine poisoning