Calcium Channel Blocker Poisoning

Description

• 3 classes of calcium channel blockers (CCBs):
  • Phenylalkylamines (verapamil):
    • Vasodilation resulting in hypotension
    • Negative chronotropic and inotropic effects: Bradycardia or inappropriately normal heart rate seen with hypotension
  • Dihydropyridine (amlodipine, nifedipine):
    • Vasodilation resulting in hypotension
    • In mild overdoses, little negative inotropic effect: Reflex tachycardia occurs
    • In larger overdoses, negative chronotropic and inotropic effects occur
    • Large amlodipine overdoses are associated with refractory vasoplegic shock
  • Benzothiazepine (diltiazem):
    • Vasodilation resulting in hypotension
    • Significantly negative inotropic and chronotrophic effects lead to bradycardia and reduced cardiac contractility
• Effects of calcium channel blockade:
  • Calcium plays key role in cardiac and smooth muscle contractility
  • CCBs prevent:
    • The entry of calcium, resulting in impaired muscle contraction
    • Reduces cardiac and vascular smooth muscle contractility
    • The normal release of insulin from pancreatic islet cells, resulting in hyperglycemia
  • Nondihydropyridine CCBs (diltiazem, verapamil) reduce depolarization of the SA and AV nodes:
    • Reduces heart rate