Atenolol for Cats

Written By Leslie Ingraham
Published: 07/15/2021Updated: 07/16/2021
Atenolol for Cats

Atenolol is a heart medication, a beta-blocker used in cats to regulate cardiac rhythm and treat functional problems, such as inadequate blood pumping by the heart muscles. Atenolol slows the heart rate and lowers blood pressure, two issues involved with cardiac disease. Increased heart rate and high blood pressure are also associated with an overactive thyroid and arrhythmias (heart rhythm problems). Atenolol also treats other heart problems, such as an enlarged heart.



Atenolol is distributed in several forms, including liquids that average around $32.95, tablets at $.17 apiece, transdermal ointments at $24.95, and chews at $26.70.The drug price may differ depending on where it is purchased. Atenolol is a prescription-only medication. 


The typical dose of atenolol for cats is:

Alternative doses used with tablets include:

  • ¼ of a 25 mg tablet every day for 3 days, followed by ¼ tablet every 12 hours, or
  • ½ tab in the morning, ¼ to ½ tablet in the evening

Dosage Instructions 

The number of preparations available for atenolol for cats allows for a variety of dosage and administration instructions. Oral forms, including tablets, capsules and liquid, will require some cooperation from the cat or the help of a friend. 

If using tablets or capsules, place well back on the cat’s tongue. If administering a liquid formulation, expect the cat to spit some liquid out. There’s no need to give them more to make up for that. Many cats prefer the chicken-flavored medicated chew, and accept the oral paste in the mouth. You can give oral medications with or without food, and the therapeutic effect should appear in 1 or 2 hours. Your veterinarian may do lab tests to determine the drug’s effectiveness in your cat. A transdermal gel is given by spreading a stripe between their shoulder blades so they cannot lick it off. 

Atenolol for cats is used “off-label,” meaning that the FDA has not put it through its rigorous testing for use in animals like they have for humans. For this reason, it’s essential to follow the dosing and other instructions from your veterinarian precisely, because the drug’s label may differ. The drug stops working within 24 hours of discontinuing it; this time is longer in cats with kidney or liver disease. It is a medication that must be tapered off to avoid a severe shock to the cat’s system. 


Atenolol, also known by its brand name Tenormin, is effective for several heart diseases. They include myocardial infarction (heart attack from lack of blood flow to the heart itself), irregular heartbeats, congestive heart failure and an enlarged heart that cannot function properly. 

A symptom of an overactive thyroid (hyperthyroidism) is high blood pressure and a too-fast heart rate (more than 100 beats per minute). Atenolol is effective against both of these symptoms of hyperthyroidism. 


Side Effects 

Side effects with atenolol for cats are more frequent in older and medically unstable animals. They can include:

  • Too slow heart rate (bradycardia)
  • Disturbances in the electrical conduction system that regulates heart rhythm and speed
  • Low blood pressure
  • Depression
  • Loss of appetite
  • Diarrhea
  • Fatigue

In senior cats who have severe heart disease, additional side effects of atenolol include:

  • Difficulty breathing
  • Worsening heart failure
  • Lowered blood sugar
  • Cough
  • Collapse


Atenolol is a powerful medication that can cause severe effects if given incorrectly, and has several drug interactions. If a cat is about to have surgery, it will be essential to stop atenolol to avoid interaction with several anesthetic agents. 

Veterinarians should monitor cats who are taking atenolol to be sure the drug isn’t causing problems, including watching their blood pressure, heart rate and rhythm. Do this monitoring at home between visits to the vet, if possible. 

Veterinarians treating cats with vascular disease, a slow heart rate, or diabetes should use caution when considering atenolol. This drug may also affect the fetus if used during pregnancy, or if the cat has kidney or liver dysfunction. 

Drug Interactions

Several drugs that cause unwanted interactions with atenolol include:

  • Sympathomimetics (metaproterenol, terbutaline, epinephrine, phenylpropanolamine)
  • Anesthetic drugs (methoxyflurane, trichloroethylene)
  • Phenothiazines (chlorpromazine, fluphenazine, mesoridazine, prochlorperazine, thioridazine)
  • Anti-hypertensives (reserpine, clonidine)

Allergic Reactions and Sensitivity

There have been no reported allergies or sensitivities with atenolol.

Frequently Asked Questions 

What if I miss a dose? 

If you miss a dose of atenolol for cats, administer another dose immediately, unless it is less than 6 hours until the next dose. In that case, wait and give them their next dose on time. Do not give your cat a double-dose of this medication. 

How do I store atenolol? 

It is best to store atenolol at room temperature away from light, heat and moisture. Check the label on the bottle of liquid for correct storage. 

What if my cat overdoses on atenolol?

If you believe your cat has accidentally overdosed on atenolol, seek emergency veterinary attention immediately. Signs of a drug overdose can include vomiting, diarrhea, trouble breathing, changes in energy level, and seizures.
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