Vetdrugs 2.0Atenolol is a relatively beta-1-selective adrenergic blocker used in veterinary cardiology to slow heart rate and reduce sympathetic stimulation of the myocardium. It is used for selected tachyarrhythmias and specific structural cardiac conditions where reduced rate or contractility is desirable. Renal elimination contributes importantly to its disposition.
In cats, applications include selected hypertrophic cardiomyopathy cases and control of hyperthyroid cardiovascular signs. Oral and transdermal delivery have different exposure profiles, with inconsistent absorption reported for transdermal feline preparations.
Group
Beta1-selective adrenergic blocker
Mechanism of Action
Atenolol competitively blocks beta-1 receptors in cardiac tissue, reducing the response to catecholamines. This slows sinus-node firing, reduces atrioventricular nodal conduction and decreases myocardial contractility. Lower rate and contractile work reduce myocardial oxygen demand and can limit some adrenergically driven tachyarrhythmias.
Beta-1 blockade in the kidney can reduce renin release, contributing to effects on blood pressure and the renin–angiotensin–aldosterone system. Its antihypertensive effect is not necessarily sufficient for every veterinary hypertension case, particularly feline systemic hypertension.
Receptor selectivity is relative and can diminish at higher exposure, so beta-2-related effects remain possible. The same negative chronotropic and inotropic actions that can be useful in selected patients can worsen bradycardia or low-output states; they are not universally beneficial simply because cardiac disease is present.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Cardiovascular rate control | 0.25–1 mg/kg | PO | Every 12–24 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure; A starting approach is 1 mg/kg every 12 hours followed by reduction to response. |
| Cardiovascular rate control - fixed alternative | 6.25–12.5 mg/animal | PO | Every 12–24 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure |
| Cardiovascular rate control - selected higher dose | 3 mg/kg | PO | Every 12–24 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure; Selected conditions only; adjust to heart-rate response. |
| Subaortic or pulmonary stenosis | 0.5–1 mg/kg | PO | Every 12 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure |
| Arrhythmia - lower-dose alternative | 0.3–0.6 mg/kg | PO | Every 12 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure; For refractory ventricular tachycardia, mexiletine 5–8 mg/kg PO every 8 hours is a described adjunct. |
| Pulmonic stenosis with syncope | 0.25–1 mg/kg | PO | Every 12 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure |
| Hypertension adjunct | 0.25–1 mg/kg | PO | Every 12 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Cardiovascular rate control | 1–2 mg/kg | PO | Every 12 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure |
| Cardiovascular rate control - fixed alternative | 6.25–12.5 mg/animal | PO | Every 12–24 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure |
| Cardiac disease - higher-dose alternative | 3 mg/kg | PO | Every 12 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure; Distinct from the lower weight-based and fixed regimens; titrate to cardiovascular response. Not monotherapy for primary hypertension. |
Ferret
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Hypertrophic cardiomyopathy | 3.13–6.25 mg/animal | PO | Every 24 h | Do not use in: Sinus bradycardia, Advanced AV block, Decompensated heart failure |
Indications
- Selected supraventricular tachyarrhythmias and conditions requiring reduction of sinus rate or atrioventricular conduction.
- Selected feline hypertrophic cardiomyopathy cases with clinically relevant tachycardia or dynamic outflow obstruction.
- Control of cardiovascular signs associated with feline hyperthyroidism while the endocrine disorder is treated.
- Selected canine subaortic or pulmonary stenosis cases requiring reduced adrenergic stimulation, myocardial work or arrhythmia control.
- Adjunctive blood-pressure control in selected patients with systemic hypertension.
Contraindications
- Use cautiously in airway disease, myocardial failure, low cardiac reserve and conduction disturbances.
- Do not use alone for primary feline hypertension.
- Overt decompensated heart failure, sinus bradycardia, greater-than-first-degree AV block or beta-blocker hypersensitivity.
- Use cautiously in significant renal insufficiency and labile diabetes; hypoglycemia or thyrotoxicosis signs may be masked.
Interactions
- Other negative chronotropes or negative inotropes can increase bradycardia and cardiac depression.
- Myocardial-depressant anesthetics, calcium-channel blockers and other hypotensive agents have additive effects.
- Can worsen rebound hypertension after clonidine withdrawal; sympathomimetics may mutually reduce effectiveness.
Adverse effects
- Bradycardia and heart block.
- Bronchospasm in susceptible animals.
- Hypotension, lethargy, reduced appetite, syncope or worsening heart failure.
- Hypoglycemia or hyperglycemia can occur.
Toxicity
Overdose can cause bradycardia, hypotension, bronchospasm, heart failure and glucose or potassium abnormalities. Monitor ECG, blood pressure, glucose and potassium; supportive cardiovascular treatment and pacing may be required.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Atenolol 25 mg tablet | Tablet | 25 mg / tablet | PO |
| Atenolol 50 mg tablet | Tablet | 50 mg / tablet | PO |
| Atenolol 100 mg tablet | Tablet | 100 mg / tablet | PO |
| Agiten atenolol 50 mg tablet | Tablet | 50 mg / tablet | PO |
Monitoring and Administration
Monitor heart rate and rhythm and adjust to the desired response. Amlodipine may be combined when feline hypertension also requires treatment.
Store tightly sealed at room temperature. Compounded suspensions have reported stability of 14 days, with some specific preparations stable for 60 days; do not assume these periods apply to every compound.
Withdraw chronic atenolol gradually. Monitor blood pressure as well as cardiac rate and rhythm. A 2 mg/mL suspension in equal Ora-Plus and Ora-Sweet SF is stable for 90 days at 5°C or 25°C; sugar-containing vehicles can reduce potency below 90% within 7–14 days. Protect from light. General permission to split a tablet does not establish equal-dose divisions for every brand.