Drug Classification & Information

Atenolol is classified as a beta blocker (class II anti-arrhythmic agent).  It primarily acts on beta-1 receptors but does have weak effects on beta-2 receptors.  Beta receptors are what respond to adrenaline.  Never stop this medication suddenly unless directed to do so by a veterinarian.

Indications for Use

Atenolol is prescribed to treat irregular heart rhythms (arrhythmia).  It has been used to treat animals with both supraventricular and ventricular arrhythmias.  It is also used in animals with subaortic and pulmonic stenosis to slow the heart rate and lessen workload on the heart muscle.  It is also used in cats to treat hypertrophic obstructive cardiomyopathy.  It may occasionally be used to treat systemic hypertension.

Potential Drug Interactions

Atenolol should be used with caution with other medications that may lower the blood pressure as it may cause an additive drop in blood pressure (calcium channel blockers, ACE inhibitors).  Should also be used with caution in medications that may also slow the heart rate as it may cause significant bradycardia (such as calcium channel blockers, amiodarone, digoxin).

Drug Side Effects

Atenolol should be used in caution in a patient with a history of CHF or in those patients with reduced heart strength such as dilated cardiomyopathy.  Side effects may include lethargy, weakness or a reduction in appetite.  Can result in blood sugar abnormalities so should be used with caution in patients with Diabetes.  May cause bronchoconstriction so should be used with caution in patients with airway disease (feline asthma, chronic bronchitis).

Therapeutic Monitoring

When used to treat arrhythmias, periodic electrocardiograms (ECGs) and Holter monitors are recommended to ensure treatment efficacy. 

Dosage Forms

Human: 25, 50 and 100 mg tablets