• Commonly prescribed for: Supraventricular tachyarrhythmias, premature ventricular contractions (PVCs), and systemic hypertension
  • Species: Dogs and Cats
  • Therapeutic Class: Beta-blocker

Basic Information:

Atenolol is a beta-adrenergic blocker that effectively manages various cardiovascular conditions in veterinary medicine. It functions by diminishing the heart's workload and reducing oxygen demand by blocking the action of adrenaline on the heart. This results in a slower heart rate, decreased force of heart contractions, and lowered blood pressure.

Uses in Dogs and Cats:

  • Dogs: Atenolol is frequently used in dogs to treat heart rhythm abnormalities, such as supraventricular tachyarrhythmias and PVCs. It is also effective in managing hypertension and certain heart diseases that cause an increased heart rate or forceful heart contractions.
  • Cats: For cats, atenolol is primarily indicated for hypertrophic cardiomyopathy and other conditions that lead to increased heart muscle mass and decreased chamber size. It helps slow down the heart rate and reduces the risk of severe arrhythmic events. Atenolol is also used in managing high blood pressure, especially in cases related to hyperthyroidism.

Side Effects:

  • Common: Bradycardia (slow heart rate), hypotension (low blood pressure), lethargy, and weakness.
  • Less common: Gastrointestinal upset, such as nausea or loss of appetite, and potential exacerbation of existing heart failure in cases where not appropriately managed.


Careful dosing and monitoring are crucial, especially in animals with existing heart failure or pulmonary disease. Atenolol should not be stopped suddenly as this can lead to rebound hypertension or worsening heart conditions. Regular monitoring of heart rate and blood pressure is essential during treatment. Caution is advised when using in animals with respiratory conditions like asthma due to potential respiratory side effects.

Drug Interactions:

Atenolol may interact with other heart medications such as digitalis, calcium channel blockers, and other beta-blockers, potentially leading to additive effects on heart rate and blood pressure. It should be used cautiously with drugs that lower blood pressure or those that can alter electrolyte balance.


  • Overdosing on atenolol can result in severe bradycardia, hypotension, heart failure, and cardiac arrest.
  • Immediate veterinary attention is necessary, involving symptomatic and supportive treatment, including IV fluids, atropine for bradycardia, and vasopressors if needed to maintain blood pressure.