Calan tablets are indicated for the treatment of the following:

Verapamil HCl tablets are contraindicated in:Severe left ventricular dysfunction (see Warnings)Hypotension (systolic pressure less than 90 mm Hg) or cardiogenic shockSick sinus syndrome (except in patients with a functioning artificial ventricular pacemaker)Second- or third-degree AV block (except in patients with a functioning artificial ventricular pacemaker)Patients with atrial flutter or atrial fibrillation and an accessory bypass tract (eg, Wolff-Parkinson-White, Lown-Ganong-Levine syndromes).

(See Warnings.)Patients with known hypersensitivity to verapamil hydrochloride.

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Left Ventricular Dysfunction -- A condition in which the LEFT VENTRICLE of the heart was functionally impaired. This condition usually leads to HEART FAILURE; MYOCARDIAL INFARCTION; and other cardiovascular complications. Diagnosis is made by measuring the diminished ejection fraction and a depressed level of motility of the left ventricular wall.

Syndrome -- A symptom complex of unknown etiology, that is characteristic of a particular abnormality.

Complete atrioventricular block -- Complete failure of atrial electrical impulse conduction through the AV node to the ventricles.

Atrial Flutter -- Rapid, irregular atrial contractions caused by a block of electrical impulse conduction in the right atrium and a reentrant wave front traveling up the inter-atrial septum and down the right atrial free wall or vice versa. Unlike ATRIAL FIBRILLATION which is caused by abnormal impulse generation, typical atrial flutter is caused by abnormal impulse conduction. As in atrial fibrillation, patients with atrial flutter cannot effectively pump blood into the lower chambers of the heart (HEART VENTRICLES).

Atrial Fibrillation -- Abnormal cardiac rhythm that is characterized by rapid, uncoordinated firing of electrical impulses in the upper chambers of the heart (HEART ATRIA). In such case, blood cannot be effectively pumped into the lower chambers of the heart (HEART VENTRICLES). It is caused by abnormal impulse generation.

Lown-Ganong-Levine Syndrome -- A form of ventricular pre-excitation characterized by a short PR interval and a normal QRS complex. In this syndrome, the atrial impulse conducts via the James fibers which connect the atrium to BUNDLE OF HIS bypassing the upper ATRIOVENTRICULAR NODE. HEART VENTRICLES are depolarized normally through the His-Purkinje system.

Hypersensitivity -- Altered reactivity to an antigen, which can result in pathologic reactions upon subsequent exposure to that particular antigen.

Verapamil has a negative inotropic effect, which in most patients is compensated by its afterload reduction (decreased systemic vascular resistance) properties without a net impairment of ventricular performance.

In clinical experience with 4,954 patients, 87 (1.8%) developed congestive heart failure or pulmonary edema.

Verapamil should be avoided in patients with severe left ventricular dysfunction (eg, ejection fraction less than 30%) or moderate to severe symptoms of cardiac failure and in patients with any degree of ventricular dysfunction if they are receiving a beta-adrenergic blocker (see Drug interactions).

Patients with milder ventricular dysfunction should, if possible, be controlled with optimum doses of digitalis and/or diuretics before verapamil treatment.

(Note interactions with digoxin under Precautions.)