Medicine & USMLE

Non-DHP Calcium Channel Blockers (Old)

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Non-DHP calcium channel blockers include the drugs diltiazem and verapamil. These drugs are myocardium selective, meaning they act specifically to block calcium channels in the heart. Clinically, these drugs are used to treat supraventricular tachycardias like atrial fibrillation. Common side effects include bradycardia, heart block, and constipation. Be sure to remind your patients to stay away from grapefruit juice while on this medication.

Key Points

  • Key Drugs
    • Diltiazem
    • Verapamil
    • Mechanism
      • Myocardium selective
      • Decrease contractility
        • Blocks calcium channels in the myocardium, decreasing the strength of cardiac muscle contraction and thus decreasing the oxygen demand of the heart.
      • Decrease heart rate
        • Blocks calcium channels within the SA and AV nodes, slowing the rate of conduction and decreasing the heart rate.
    • Clinical Use
      • Dysrhythmias
        • Supraventricular Tachycardia (SVT)
        • Atrial fibrillation
          • Does not convert atrial fibrillation to sinus rhythm, but can help control ventricular rate.
      • Angina
      • Hypertension
    • Side Effects and Adverse Reactions
      • Bradycardia
        • A suppression of cardiac activity can cause bradycardia, as well as heart block and heart failure.
          • Contraindicated in patients with current bradycardia or heart blocks.
        • Check pulse prior to administration
        • Can result in hypotension
      • Avoid grapefruit juice
        • Increases the amount of drug levels in the body by inhibiting liver enzymes responsible for drug breakdown
        • Can lead to severe cardiac depression
      • Constipation
        • Encourage a high fiber diet