Atenolol: veterinary dose and monograph

At a glance

Drug class

Cardiovascular

Also known as

Tenormin

Species with doses

Dogs, Cats and Ferrets

General dose range

0.25–2 mg/kg PO q12–24h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Feline hypertrophic cardiomyopathy with outflow obstruction
• Supraventricular tachyarrhythmia / rate control
• Tachycardia / agitation of feline hyperthyroidism (bridge to definitive therapy)

Atenolol dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• SVT / rate control: Papich 5e: 0.25–1 mg/kg q12–24h PO (6.25–12.5 mg per dog), commonly starting at 1 mg/kg q12h and reducing to the optimum heart rate; up to 3 mg/kg for some conditions. Plumb’s p.119: 0.3–0.6 mg/kg q12h (Smith 2009); sub-aortic stenosis 0.5–1 mg/kg twice daily; pulmonic stenosis and hypertension 0.25–1 mg/kg twice daily.

Cats

• HCM / hyperthyroid tachycardia: Papich 5e: 1–2 mg/kg q12h PO; because of tablet size commonly 6.25–12.5 mg per cat (¼–½ of a 25 mg tablet) q12–24h. Plumb’s p.119: 6.25–12.5 mg per cat q12h (Kittleson; Stepien) or q12–24h — treatment of choice for hyperthyroid hypertensive cats (Waddell 2005).

Ferrets

• Hypertrophic cardiomyopathy: Plumb’s p.119: 6.25 mg per ferret PO once daily (Williams 2000); 3.13–6.25 mg once daily (Johnson-Delaney 2005).

Contraindications

Decompensated / congestive heart failure, bradyarrhythmia / AV block, hypotension. Reactive airway disease (relatively β1-selective but caution). Abrupt withdrawal (taper to avoid rebound). Caution in diabetics (masks hypoglycaemia).

Adverse effects

• Bradycardia, hypotension, lethargy
• Worsening of overt heart failure
• Bronchoconstriction (high dose)

Drug interactions

• Calcium-channel blockers (diltiazem, verapamil): additive bradycardia, AV block and negative inotropy — combine cautiously
• Other antihypertensives: additive hypotension
• Insulin / oral hypoglycaemics: masks the adrenergic signs of hypoglycaemia
• Alpha-2 agonists / clonidine: rebound hypertension if either drug is withdrawn

Pregnancy and lactation

Crosses the placenta; beta-blockers can cause foetal bradycardia and growth effects — use in pregnancy only if necessary.

Monitoring

• Heart rate and blood pressure — titrate to a target heart rate
• Reassess for signs of decompensating heart failure
• Echo / outflow gradient in HCM cases; taper on discontinuation

Toxicity and overdose

Overdose causes bradycardia, hypotension, AV block, heart failure and bronchospasm. Cardiac depression can be severe even though atenolol has less CNS effect than lipophilic beta-blockers.

Management: Atropine for bradycardia; IV fluids and vasopressors / dobutamine for hypotension; GLUCAGON (1–5 mg, or per weight) is the specific reversal for beta-blocker cardiotoxicity; consider high-dose insulin–euglycaemia therapy and pacing for refractory cases.

Clinical pearls

• Avoid in any patient that is in (or close to) congestive failure — a beta-blocker can tip them over
• Useful short-term in the hyperthyroid cat to calm tachycardia / hypertension before radioiodine or surgery
• Taper rather than stop abruptly to avoid rebound tachycardia / hypertension

Mechanism of action

Cardioselective β1-adrenergic antagonist. Blocks cardiac β1 receptors to reduce heart rate, AV-nodal conduction, contractility and myocardial oxygen demand, and to attenuate dynamic left-ventricular outflow obstruction. Hydrophilic, with little CNS penetration.

Formulations and products

• Atenolol 25 mg tablet
• Atenolol 50 mg tablet
• Atenolol 100 mg tablet
• Tenormin — 25 / 50 / 100 mg, Tablet (human-label)
• Aten — 25 / 50 / 100 mg, Tablet (human-label)

Storage

Store at 15–30 °C, dry.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other cardiovascular drugs

• Amiodarone
• Amlodipine
• Benazepril
• Captopril
• Carvedilol
• Digoxin
• Diltiazem
• Dobutamine

Frequently asked questions