Pharm

Verapamil

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Verapamil, Calan, Phenylalkamine, Verelan, Isoptin SR

  • See Also
  1. Calcium Channel Blocker
  2. Calcium Channel Blocker Overdose
  3. Dihydropyridine Calcium Channel Blocker (e.g. Amlodipine, Nifedipine)
  4. Diltiazem
  5. Mibefradil
  • Mechanism
  1. Non-Dihydropyridine Calcium Channel Blocker
  2. AV Node effects
    1. Slow AV Node Conduction
    2. Prolong AV Node refractory period
  3. Reduces myocardial Oxygen Consumption
    1. Negative chronotropic effect
    2. Negative inotropic effect
  4. Reduces Systemic Vascular Resistance
    1. Results from vasodilatation of peripheral arteriole vascular Smooth Muscle
    2. Counters negative inotropic effect
  5. More negative hemodynamic effects than Diltiazem
  6. Coronary vasodilatation
  • Indications
  1. Diltiazem is typically the preferred Non-Dihydropyridine Calcium Channel Blocker
  2. Paroxysmal Supraventricular Tachycardia (90% effective)
    1. Terminates sustained reentry within AV Node
    2. Terminates AV Node limb of reentrant circuit
  3. 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
  4. Hypertension
    1. Consider Dihydropyridine Calcium Channel Blocker (e.g. Amlodipine) instead if Heart Rate control not needed
  5. Angina
    1. Decreases Anginal episodes
  • 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 or LV Dysfunction
  5. Concurrent Intravenous Beta Blocker use
  1. Initial Dose: 2.5 to 5.0 mg (0.075 to 0.15 mg/kg) IV bolus over 2 to 3 min
  2. Subsequent: 5 to 10 mg IV every 15 to 30 min
  3. Maximum 30 mg total, cummulative dose
  1. Initial: 0.1 mg/kg up to 2.5 to 5 mg IV over 1-2 min
  2. Subsequent: 0.2 mg/kg up to 5 to 10 mg after 15 to 30 min
  3. Dose range: 0.1 to 0.3 mg/kg IV
  1. Do not chew or crush medication
    1. However scored tablets may be cut
    2. Sustained release capsules may be sprinkled on food
  2. Regular Release
    1. Start 40 to 80 mg orally three times daily
    2. Maximum 480 mg/day
  3. Extended Release
    1. Isoptin SR and Calan SR should be divided twice daily when daily dose >240 mg/day
    2. Start 120 to 240 mg orally daily
    3. Maximum 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
  • Adverse Effects
  1. See Calcium Channel Blocker
  2. Constipation (more than with Diltiazem)
  3. Peripheral Edema
  4. Congestive Heart Failure exacerbation
  5. Hypotension
  6. Bradycardia
  7. Gastrointestinal upset or Nausea
  8. Dizziness
  • Safety
  1. Pregnancy Category C
  2. Avoid in Lactation
  • Drug Interactions
  1. Agents that prolong AV Node conduction (avoid)
    1. Beta Blockers
    2. Digoxin
    3. Clonidine (case reports of severe episodes)
    4. Ivabradine (contraindicated in combination)
  2. Agents with levels increased by Verapamil
    1. Digoxin (increases level >50%)
    2. Lovastatin (limit to 20 mg daily)
    3. Simvastatin (limit to 10 mg daily)
    4. Doxorubicin
  3. Agents that increase Verapamil levels
    1. Grapefruit Juice
    2. Cimetidine (reduces clearance)
  4. Other interactions
    1. Chemotherapy
    2. mTOR Inhibitors (e.g. Sirolimus)
    3. Prazosin (Hypotension)
    4. Calcium Supplement (inhibits Verapamil activity)
  • Pharmacokinetics
  1. Peak effect seen within 3-5 minutes of bolus injection
  2. Serum half life 5 hours
    1. Prolonged up to 20 hours in Cirrhosis
  • Metabolism
  1. Well absorbed orally
  2. First pass metabolism 80% to active metabolites
  3. Highly Protein bound (90%)
  4. Exercise caution in liver or renal Impairment
  • Resources
  1. Verapamil Tablet (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ed1e0c14-3571-43f9-88fc-5a4d2b598263
  2. Verapamil Delayed Release Tablet (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0742cf97-601b-4c13-a6c3-1a6a616ed292
  3. Verapamil Injection Solution (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=df77b8d1-1d2b-4fea-a1e9-153bd25008a6
  • References
  1. (2022) Presc Lett, Resource #381108, Comparison of Calcium Channel Blockers
  2. (2020) Med Lett Drugs Ther 62(1598): 73-80
  3. Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 70-1
  4. Hamilton (2020) Tarascon Pocket Pharmacopoeia