Calcium Channel Blocker Poisoning



  • 3 classes of calcium channel blockers (CCBs):
    • Phenylalkylamines (verapamil):
      • Vasodilation resulting in a decrease in BP
      • Negative chronotropic and inotropic effects: Reflex tachycardia not seen with a drop in BP
    • Dihydropyridine (nifedipine):
      • Decreased vascular resistance resulting in a drop in BP
      • Little negative inotropic effect: Reflex tachycardia occurs
    • Benzothiazepine (diltiazem):
      • Decreased peripheral vascular resistance leading to a decrease in BP
      • Heart rate (HR) and cardiac output initially increased
      • Direct negative chronotropic effect, which leads to a fall in HR
  • Effects of calcium channel blockade
    • Calcium plays key role in cardiac and smooth muscle contractility
    • CCBs prevent:
      • The entry of calcium, resulting in a lack of muscle contraction
      • The normal release of insulin from pancreatic islet cells, resulting in hyperglycemia

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