Name

verapamil (Isoptin®, Calan®)

Class

Calcium Channel Blocker (Class IV antidysrhythmic)

Description/Mechanism

Verapamil is used as an antidysrhythmic and antianginal agent. It works by inhibiting the movement of calcium ions across cell membranes.

The slow calcium ion current blocked by verapamil is more important for the activity of the SA node and AV node than for any other tissues in the heart. By interfering with this current, calcium channel blockers achieve some selectivity of action.

Verapamil decreases atrial automaticity, reduces AV conduction velocity, and prolongs the AV nodal refractory period. In addition, verapamil depresses myocardial contractility, reduces vascular smooth muscle tone, and dilates coronary arteries and arterioles in normal and ischemic tissues.

Onset

2-5 minutes

Duration

30-60 minutes

Indications

PSVTs

Atrial flutter with a rapid ventricular response

Atrial fibrillation with a rapid ventricular response

Contraindications

Hypersensitivity

Sick sinus syndrome (unless the patient has a functioning pacemaker)

Second- or Third degree heart block

Hypotension

Cardiogenic shock

Severe CHF

WPW with atrial fibrillation or flutter

Patients receiving intravenous beta blockers

Wide complex tachycardias (VT can deteriorate into VF when calcium channel blockers are given)

Adverse Reactions

Dizziness

Headache

Nausea and vomiting

Hypotension

Bradycardia

Complete AV block

Peripheral edema

Drug Interactions

Verapamil increases serum concentrations of digoxin

Beta adrenergic blockers may have additive negative inotropic and chronotropic effects

Antihypertensives may potentiate hypotensive effects

Supplied

5mg/2 ml in 2,4,5 ml vials or 2,4 ml ampules

Dose/Administration

Adult

IV: Initial dose: 2.5 – 5 mg slow bolus over 1-2 minutes (1-3 mg in elderly patients).

Repeat dose: 5-10 mg in 15-30 minutes or 5 mg every 15 minutes until desired response (max 30 mg dose)

Pediatric

Not recommended

Special Consideration

Pregnancy Safety: Category C

Closely monitor patient’s vital signs

Give smaller amounts (2-4 mg) over longer periods of time (3-4 minutes) when treating the elderly or when the blood pressure is in the lower range of normal

Be prepared to resuscitate

AV block or asystole may occur due to slowed AV conduction.

Note: Many physicians recommend slow IV administration of 500 mg calcium chloride prior to verapamil to minimize the untoward results of hypotension and bradycardia.