home > drugs a-z list > calan (verapamil hcl) drug center > calan (verapamil hcl) drug - overdosage and contraindications

Treat all verapamil overdoses as serious and maintain observation for at least 48 hours (especially CALAN SR), preferably under continuous hospital care. Delayed pharmacodynamic consequences may occur with the sustained-release formulation. Verapamil is known to decrease gastrointestinal transit time.

Treatment of overdosage should be supportive. Beta-adrenergic stimulation or parenteral administration of calcium solutions may increase calcium ion flux across the slow channel and have been used effectively in treatment of deliberate overdosage with verapamil. In a few reported cases, overdose with calcium channel blockers has been associated with hypotension and bradycardia, initially refractory to atropine but becoming more responsive to this treatment when the patients received large doses (close to 1 gram/hour for more than 24 hours) of calcium chloride. Verapamil cannot be removed by hemodialysis. Clinically significant hypotensive reactions or high degree AV block should be treated with vasopressor agents or cardiac pacing, respectively. Asystole should be handled by the usual measures including cardiopulmonary resuscitation.

Verapamil HCl tablets are contraindicated in:

1. Severe left ventricular dysfunction (see WARNINGS)
2. Hypotension (systolic pressure less than 90 mm Hg) or cardiogenic shock
3. Sick sinus syndrome (except in patients with a functioning artificial ventricular pacemaker)
4. Second- or third-degree AV block (except in patients with a functioning artificial ventricular pacemaker)
5. Patients with atrial flutter or atrial fibrillation and an accessory bypass tract (eg, Wolff-Parkinson-White, Lown-Ganong-Levine syndromes) (see WARNINGS)
6. Patients with known hypersensitivity to verapamil hydrochloride

Last reviewed on RxList: 11/9/2011
This monograph has been modified to include the generic and brand name in many instances.