Atenolol is a beta-1 selective adrenergic blocking agent (beta-blocker) widely used in feline cardiology for the management of hypertrophic cardiomyopathy (HCM), the most common heart disease in cats. By blocking beta-1 receptors in the heart, atenolol slows the heart rate, reduces myocardial oxygen demand, and may improve diastolic filling — all of which are beneficial in cats with thickened heart muscle.
Overview
Hypertrophic cardiomyopathy affects an estimated 15 percent of cats, with certain breeds (Maine Coon, Ragdoll, British Shorthair, Sphynx) at higher genetic risk. The hallmark of HCM is abnormal thickening of the left ventricular wall, which can lead to impaired relaxation (diastolic dysfunction), dynamic left ventricular outflow tract obstruction (LVOTO), arrhythmias, congestive heart failure, and arterial thromboembolism (ATE). Atenolol is the most commonly prescribed beta-blocker in feline HCM management because of its relative beta-1 selectivity, once- or twice-daily dosing schedule, and extensive clinical experience.
Uses
- Hypertrophic cardiomyopathy (HCM): Reduces heart rate, improves diastolic filling time, and may reduce dynamic LVOT obstruction.
- Tachyarrhythmias: Controls supraventricular and some ventricular arrhythmias by slowing conduction.
- Hyperthyroid-associated tachycardia: Controls rapid heart rate in hyperthyroid cats while awaiting definitive treatment.
- Systemic hypertension: Occasionally used as an adjunct antihypertensive, though not first-line for feline hypertension.
Dosage
| Parameter | Detail |
|---|---|
| Dose (cats) | 6.25–12.5 mg per cat orally every 12–24 hours |
| Common starting dose | 6.25 mg (one quarter of a 25 mg tablet) every 12 hours |
| Route | Oral |
| Frequency | Every 12–24 hours |
| Monitoring | Heart rate, blood pressure, echocardiography, ECG |
Important dosing notes:
- Tablets can be quartered or compounded into a flavored liquid for easier dosing.
- Target resting heart rate in cats on atenolol is typically below 180–200 bpm.
- Do not abruptly discontinue atenolol; taper gradually under veterinary guidance to avoid rebound tachycardia.
- Cats with congestive heart failure should not start atenolol until heart failure is stabilized, as beta-blockers can worsen acute CHF.
Side Effects
| Common Side Effects | Serious Side Effects (Contact Your Vet) |
|---|---|
| Mild lethargy | Severe bradycardia (dangerously slow heart rate) |
| Decreased appetite | Hypotension (weakness, collapse) |
| Mild GI upset | Worsening of congestive heart failure signs (labored breathing, coughing) |
| Cold extremities (ears, paws) | Syncope (fainting) |
| Bronchospasm (rare; problematic in cats with concurrent asthma) |
Most cats tolerate atenolol well at standard doses. Side effects are dose-dependent and generally manageable.
Drug Interactions
- Calcium channel blockers (diltiazem): Additive negative chronotropic and inotropic effects; use together only under close cardiologist supervision.
- Albuterol (inhaled bronchodilator): Beta-blockers may reduce the effectiveness of albuterol. Cats with both HCM and asthma require careful drug selection.
- Amlodipine: Generally safe to combine for blood pressure management, but monitor for excessive hypotension.
- Anesthetic agents (propofol, isoflurane): Additive cardiovascular depression; inform the anesthesiologist that your cat takes atenolol.
- Insulin: Beta-blockers may mask signs of hypoglycemia (tachycardia).
- ACE inhibitors / ARBs: Commonly combined in HCM management; monitor blood pressure.
Contraindications
- Do not use in cats with acute decompensated congestive heart failure (stabilize first).
- Avoid in cats with severe bradycardia, second- or third-degree heart block, or sick sinus syndrome.
- Use with extreme caution in cats with asthma, as beta-blockers can precipitate bronchospasm.
- Use cautiously in cats with severe renal impairment (atenolol is renally excreted).
- Do not use in cats with uncontrolled diabetes without close monitoring.
- Safety in pregnant or lactating cats has not been established.
Storage
- Store at room temperature (68–77 degrees F / 20–25 degrees C).
- Protect from moisture and light.
- Compounded liquid formulations may require refrigeration; follow your pharmacy’s instructions.
- Keep out of reach of children and pets.
FAQ
Q: Does atenolol cure HCM in cats? A: No. HCM is a structural heart disease that cannot be cured with medication. Atenolol helps manage symptoms, improve cardiac function, and may reduce the risk of certain complications. Regular echocardiographic monitoring is important.
Q: My cat has both HCM and asthma. Can atenolol be used? A: This is a challenging clinical scenario. While atenolol is beta-1 selective (primarily affecting the heart), at higher doses it can also block beta-2 receptors in the airways, potentially worsening asthma. Your veterinarian or a veterinary cardiologist will carefully weigh the risks and benefits and may consider alternatives.
Q: How often does my cat need echocardiograms while on atenolol? A: Your veterinarian or cardiologist will typically recommend echocardiographic reassessment every 6 to 12 months, or sooner if clinical signs change. This monitors disease progression and verifies that the medication is having the desired effect.
Q: Can I give atenolol with food? A: Yes. Atenolol can be given with or without food. Giving it with food may improve acceptance and reduce mild GI effects.
This content is for informational purposes only and is not a substitute for professional veterinary advice. Always consult your veterinarian before starting, changing, or stopping any medication for your cat.