Pharm

Verapamil

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Verapamil, Calan, Phenylalkamine

  • Mechanism
  1. AV Node effects
    1. Slow AV Node Conduction
    2. Prolong AV Node refractory period
  2. Reduces myocardial Oxygen Consumption
    1. Negative chronotropic effect
    2. Negative inotropic effect
  3. Reduces Systemic Vascular Resistance
    1. Results from vasodilatation of vascular smooth muscle
    2. Counters negative inotropic effect
  4. More negative hemodynamic effects than Diltiazem
  5. Coronary vasodilatation
  • Contraindications
  1. Wolff-Parkinson-White Syndrome with Atrial Fibrillation
    1. Paroxysmal accelerated ventricular response
    2. Risk of progression into Ventricular Fibrillation
  2. Wide Complex Tachycardia (unless supraventricular)
    1. Risk of severe Hypotension
    2. May progress into Ventricular Fibrillation
    3. Verapamil ineffective against Ventricular Tachycardia
  3. Sinus Node or AV Node dysfunction without Pacemaker
    1. AV Block
    2. Sick Sinus Syndrome
  4. Severe Congestive Heart Failure
  5. Concurrent Intravenous Beta Blocker use
  • Indications
  1. Paroxysmal Supraventricular Tachycardia (90% effective)
    1. Terminates sustained reentry within AV Node
    2. Terminates AV Node limb of reentrant circuit
  2. Supraventricular Tachycardia
    1. Terminates AV Node reentry Tachycardias
    2. Slows ventricular response to Atrial Fibrillation
    3. Verapamil is highly effective
    4. Used for acute treatment and prevention
  3. Hypertension
  • Drug Interaction
  1. Increases Digitalis (Digoxin) level
  2. Beta Blocker (see contraindications above)
  • Pharmacokinetics
  1. Peak effect seen within 3-5 minutes of bolus injection
  • Dosing
  1. Supraventricular Tachycardia
    1. Adults
      1. Initial Dose: 2.5 to 5.0 mg IV bolus over 3 min
      2. Subsequent: 5 mg IV every 15 min (Max 30 mg total)
    2. Children (8-15 years old)
      1. Initial: 0.1 mg/kg up to 2.5 mg IV over 1-2 min
      2. Subsequent: 0.2 mg/kg up to 5 mg after 15 min
  2. Hypertension
    1. Regular: 80 mg PO tid (MAX 360 mg/day)
    2. Extended: 240 mg PO qd (MAX 480 mg/day)
  1. Results from peripheral vasodilation
  2. Countered by Intravenous Calcium Injection
  3. Consider prophylactic pretreatment with Calcium
    1. Marginal Blood Pressure
    2. Left Ventricular Dysfunction