Vet Guide to Atenolol in 2025 🐾

Hello! I’m Dr Duncan Houston, BVSc, founder of Ask A Vet. In this comprehensive 2025 guide, we’ll dive into atenolol—its role as a β₁‑selective beta‑blocker for dogs and cats with heart conditions and hypertension. You’ll learn dosing, common uses, safety precautions, monitoring recommendations, and what to do in emergencies. Let’s go! ❤️

📘 What Is Atenolol?

Atenolol is a β₁‑selective beta‑adrenergic blocker (beta‑blocker) used off‑label in veterinary practice. It slows heart rate, controls arrhythmias, and can lower blood pressure in dogs and cats :contentReference[oaicite:3]{index=3}.

✅ Common Veterinary Uses in 2025

• Treating arrhythmias (e.g., atrial fibrillation, SVT, PVCs) in dogs and cats :contentReference[oaicite:4]{index=4}.
• Managing feline hypertrophic cardiomyopathy (HCM) with left‑ventricular obstruction :contentReference[oaicite:5]{index=5}.
• Controlling hyperthyroid‑related tachycardia in cats :contentReference[oaicite:6]{index=6}.
• Lowering systemic hypertension in dogs and cats :contentReference[oaicite:7]{index=7}.

📐 Dosing & Administration

Dogs

• Oral: 0.25–1.0 mg/kg once or twice daily (≈0.125–0.5 mg/lb), based on condition :contentReference[oaicite:8]{index=8}.
• Begin on lower end and titrate with veterinary monitoring :contentReference[oaicite:9]{index=9}.

Cats

• Oral: ~2 mg/kg once daily (≈1 mg/lb)—often in single morning dose :contentReference[oaicite:10]{index=10}.
• Often used specifically in HCM or hypertension scenarios :contentReference[oaicite:11]{index=11}.

🕐 How Quickly It Works

Onset occurs in 1–2 hours. Duration is roughly 24 hours in normal pets, though extended in those with renal or hepatic disease :contentReference[oaicite:12]{index=12}.

⚠️ Side Effects & Precautions

Common:

• Bradycardia (slow heart rate), lethargy, weakness :contentReference[oaicite:13]{index=13}.
• GI upset—vomiting, diarrhea, appetite reduction :contentReference[oaicite:14]{index=14}.
• Low blood pressure—collapse, dizziness :contentReference[oaicite:15]{index=15}.
• Respiratory issues in pets with bronchospastic lung disease :contentReference[oaicite:16]{index=16}.

Serious / Contraindications:

• Contraindicated in heart block beyond first degree, cardiogenic shock, overt congestive heart failure until stabilized, or severe bradycardia :contentReference[oaicite:17]{index=17}.
• Avoid or use cautiously in pets with renal disease, diabetes, asthma, GI ulcers, pregnant/nursing animals :contentReference[oaicite:18]{index=18}.
• Avoid in cats with left-sided HCM presenting signs of failure :contentReference[oaicite:19]{index=19}.

🔗 Drug Interactions

Atenolol may interact with:

• Other antihypertensives (ACE inhibitors, calcium-channel blockers), leading to additive hypotension :contentReference[oaicite:20]{index=20}.
• Antiarrhythmics (amiodarone, diltiazem, digoxin)—pressure on heart rate :contentReference[oaicite:21]{index=21}.
• Diuretics, phenylpropanolamine, corticosteroids, sympathomimetics—all require caution :contentReference[oaicite:22]{index=22}.

🩺 Monitoring Guidelines

• Recheck heart rate, blood pressure, and rhythm ~2 weeks after starting or dose adjustment :contentReference[oaicite:23]{index=23}.
• Periodic ECGs or Holter monitoring in arrhythmia/HCM cases :contentReference[oaicite:24]{index=24}.
• Monitor appetite, energy, urination, and breathing regularly.
• Routine bloodwork if renal disease or long-term use (renal clearance dependency) :contentReference[oaicite:25]{index=25}.

⏳ Missed Dose & Tapering

If you miss a dose, give it as soon as you remember—unless it's close to the next scheduled dose. Never double up :contentReference[oaicite:26]{index=26}. Do not abruptly stop—taper down under veterinary guidance to avoid rebound effects :contentReference[oaicite:27]{index=27}.

🚨 Overdose & Emergency Protocols

Overdose signs include extreme bradycardia, hypotension, collapse, or respiratory distress. Emergency care is required—possibly involving IV fluids, atropine, glucagon, and pressors. Contact your vet or emergency service immediately :contentReference[oaicite:28]{index=28}.

🏡 Practical Scenarios

🐶 Dog with SVT

• Start atenolol 0.25 mg/kg BID, check ECG in 2 weeks, adjust dose as needed.

🐱 Cat with HCM (Obstructive)

• Give ~2 mg/kg in morning dose, follow with recheck echocardiogram and heart rate monitoring.

🐱 Cat with Hypertension & Hyperthyroidism

• Administer 2 mg/kg once daily; monitor blood pressure and renal function.

❓ FAQs

Can I split doses or use liquid form?

Yes—tablets, half doses, or flavored liquid from compounding pharmacy are options. Administer with food to reduce GI upset.

Can atenolol cure HCM?

No—atenolol manages symptoms (heart rate, hypertension) but does not reverse the disease.

Should it replace pimobendan or ACE inhibitors?

No—atenolol has different action. Decisions on combination therapy depend on specific heart condition and under vet guidance.

📌 Final Takeaways

• Atenolol is a β₁‑selective beta‑blocker used off-label in dogs and cats for arrhythmias, hypertension, HCM, and hyperthyroid tachycardia.
• Dosing: 0.25–1 mg/kg once or twice daily in dogs; ~2 mg/kg once daily in cats.
• Monitor heart rate, rhythm, blood pressure, and organ function regularly, especially in at-risk patients.
• Don't abruptly stop therapy; be cautious of drug interactions and contraindicated conditions.
• Emergency signs like collapse, extreme lethargy, or breathing difficulty require immediate veterinary attention.

Need help managing heart disease or blood pressure with atenolol? Download the Ask A Vet app for tailored veterinary advice and support anytime. We’re here for your pet’s heart health! 🐾❤️