What is the dosage and usage of Verapamil (calcium channel blocker) for treating high blood pressure and heart rhythm disorders?

Verapamil Dosing and Usage for Hypertension and Arrhythmias

Hypertension Management

For essential hypertension, initiate verapamil extended-release at 180 mg once daily in the morning with food, titrating upward weekly based on blood pressure response to a maximum of 480 mg daily. 1

Initial Dosing Strategy

• Start with 120 mg daily in elderly patients or those of small stature who may have enhanced drug response 1
• Standard starting dose is 180 mg extended-release once daily taken in the morning with food 1
• Antihypertensive effects become evident within the first week of therapy 1

Titration Protocol

• Assess therapeutic efficacy weekly, measuring blood pressure approximately 24 hours after the previous dose 1
• If 180 mg is inadequate, escalate as follows: 1
  • 240 mg each morning
  • 180 mg morning plus 180 mg evening
  • 240 mg morning plus 120 mg evening
  • 240 mg every 12 hours

Maintenance Dosing

• Effective dose range: 240-360 mg daily for most patients with mild to moderate hypertension 2, 3
• Maximum daily dose: 480 mg 4, 1
• When converting from immediate-release to extended-release formulations, maintain the same total daily dose in milligrams 1

Important caveat: Research demonstrates that 480 mg daily provides no additional benefit over 360 mg daily but significantly increases side effects, particularly constipation and dizziness 5. Therefore, avoid exceeding 360 mg daily unless absolutely necessary.

Arrhythmia Management

Acute Rate Control (Intravenous)

For acute rate control in narrow-complex supraventricular tachycardias, administer 2.5-5 mg IV over 2 minutes, repeating with 5-10 mg every 15-30 minutes as needed to a maximum total dose of 20-30 mg. 4, 6

• Alternative regimen: 5 mg bolus every 15 minutes to a total of 30 mg 6
• Administer only after confirming narrow-complex tachycardia or definitively diagnosed supraventricular origin 4, 6
• Have resuscitation equipment immediately available due to hypotension risk 7

Chronic Rate Control (Oral)

For long-term rate control in atrial fibrillation, initiate at 120 mg daily and titrate to 120-480 mg daily in divided doses or as extended-release once daily. 4, 6

• Standard immediate-release dosing: 40-120 mg three times daily 6
• Extended-release formulation: 120-480 mg once daily 4, 6
• Typical maintenance range: 120-360 mg daily 6

Supraventricular Tachycardia

Verapamil serves as a third-line agent for acute SVT termination after vagal maneuvers and adenosine have failed. 7

• First-line: Vagal maneuvers 7
• Second-line: Adenosine 7
• Third-line: Verapamil (when adenosine fails or is contraindicated) 7
• For hemodynamically unstable SVT, proceed directly to synchronized cardioversion rather than pharmacotherapy 7

Absolute Contraindications

Never administer verapamil in the following situations: 4, 7

• Wide-complex tachycardias (risk of hemodynamic collapse if ventricular in origin) 4, 6
• Wolff-Parkinson-White syndrome with atrial fibrillation or flutter (may precipitate ventricular fibrillation) 4
• Decompensated heart failure or severe LV dysfunction (LVEF <40%) 4
• Second or third-degree AV block without pacemaker 4, 7
• Sick sinus syndrome without pacemaker 4
• Cardiogenic shock 4, 7
• Hypotension 4

Special Populations and Precautions

Hypertrophic Cardiomyopathy

• Verapamil up to 480 mg daily (sustained-release) improves symptoms by enhancing ventricular relaxation and reducing ischemia 4
• Critical warning: Avoid in patients with severe symptoms (orthopnea, paroxysmal nocturnal dyspnea) combined with marked outflow obstruction and elevated pulmonary pressures—deaths have been reported due to vasodilation overwhelming negative inotropic effects 4
• Contraindicated in infants due to sudden death risk with IV administration 4
• Oral dosing not established for infants and preadolescent children 4

Unstable Angina/NSTEMI

• Immediate-release verapamil: 80-160 mg three times daily 4
• Extended-release: 120-480 mg once daily 4
• Avoid in pulmonary edema or severe LV dysfunction 4
• Evidence base strongest for verapamil and diltiazem among calcium channel blockers 4

Combination Therapy Warnings

• Exercise extreme caution when combining with beta-blockers—synergistic depression of LV function, sinus node, and AV conduction may occur 4, 7
• If patient recently received beta-blockers, risk of profound bradycardia and hypotension is significantly elevated 7
• Verapamil is a moderate CYP3A4 inhibitor and P-glycoprotein inhibitor—numerous drug interactions exist including with dofetilide (contraindicated), dabigatran, rivaroxaban, and simvastatin 4

Adverse Effects Monitoring

Common adverse effects requiring monitoring: 4, 6

• Hypotension (most common)
• Bradycardia
• AV block
• Constipation (mild but frequent)
• Heart failure precipitation in predisposed patients
• Pulmonary edema in HCM patients with severe obstruction

Dosage Adjustments

• Elderly patients: Consider lower initial doses (120 mg daily) 6, 1
• Hepatic impairment: Reduce initial dose 6
• Renal impairment: Consider dose reduction 6

Clinical Pearls

• Verapamil demonstrates dose-proportional pharmacokinetics with extended-release formulations (unlike immediate-release), allowing predictable dose escalation 8
• No reflex tachycardia, orthostatic hypotension, or tolerance development occurs with verapamil, unlike many other antihypertensives 2
• Particularly effective in elderly patients and those with low plasma renin activity 2
• Preferred over beta-blockers in patients with asthma or chronic obstructive airway disease since it does not cause bronchoconstriction 2
• For hypertension refractory to monotherapy, verapamil combines effectively with diuretics, ACE inhibitors, or vasodilators like prazosin 2