Verapamil (Calan)
Purpose of Medication and Method of Action
Verapamil is indicated for the management of hypertension. It is also used to treat some forms of heart rhythm disturbances. It acts by blocking the influx of calcium into the cell. In the case of hypertension, there is a relaxation of the arteriolar smooth muscles, peripheral vasodilation, and a subsequent reduction of blood pressure.
Side Effects
The most common side effects are: constipation (7%), dizziness (3%), nausea (3%), lowered blood pressure (2.5%) and edema (swelling of ankles -2%).
Drug Interactions
Use with caution along with wither disopyramide or quinidine. Increased sensitivity to lithium and resultant side effects may occur. Verapamil may also increase the blood levels of carbamazepine (Tegretol) and carbamazine side effects. Phenobarbital may speed the metabolism of verapamil and require increased dose to maintain its effectiveness.
Cautions and Contraindications
Do not use in presence of severe left ventricular dysfunction, sick sinus syndrome or heart block.
Usual Dose
Initially, 180 mg in the morning, increasing if necessary to a maximum of 240 mg every 12 hours.
Patient Medication Information
These information sheets do not list all known side effects of the medications, only the most common side effects. For a complete list of side effects please contact your local pharmacy or the actual drug manufacturing company.