Atenolol
Atenolol slows heart rate and AV conduction and is used in selected cardiac conditions in dogs and cats. Renal elimination makes kidney function relevant to dose selection.
Control of hyperthyroid-associated tachycardia does not treat the underlying thyroid disorder and may mask its cardiovascular signs.
Group
Beta-1 adrenergic blocker
Mechanism of Action
Preferential beta-1 receptor antagonism reduces sympathetic cardiac stimulation, sinus rate and AV nodal conduction. Selectivity decreases at higher exposure.
Dose Rates
Dog
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Cardiac rate control | 0.25–1 mg/kg | PO | Every 12 h | Start toward the lower end and titrate to rate, blood pressure and cardiac reserve. |
| Cardiac arrhythmia | 0.3–0.6 mg/kg | PO | Every 12 h | For refractory ventricular tachycardia, mexiletine may be added as a separate drug. |
| Subaortic stenosis | 0.5–1 mg/kg | PO | Every 12 h | Moderate to severe subvalvular aortic stenosis; titrate to hemodynamic tolerance. |
| Pulmonic stenosis-associated syncope | 0.25–1 mg/kg | PO | Every 12 h | |
| Hypertension | 0.25–1 mg/kg | PO | Every 12 h |
Cat
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Cardiac rate control | 1–2 mg/kg | PO | Every 12 h | Titrate gradually; twice-daily dosing generally provides more continuous beta blockade. |
| Cardiac rate control | 6.25–12.5 mg/animal | PO | Every 12 h | Alternative to the weight-based regimen, not an additional dose. |
| Cardiac rate control | 3 mg/kg | PO | Every 12 h | Higher weight-based alternative; not an addition to the fixed 6.25–12.5 mg regimen. Monitor heart rate and blood pressure. |
| Cardiac rate control | 6.25–12.5 mg/animal | PO | Every 12–24 h | Alternative interval; beta blockade alone may not control non-thyroidal hypertension. |
Ferret
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Hypertrophic cardiomyopathy | 3.13–6.25 mg/animal | PO | Every 24 h |
Indications
- Selected tachyarrhythmias requiring rate control.
- Selected feline hypertrophic cardiomyopathy or hyperthyroid-associated tachycardia.
- Selected congenital outflow-obstruction conditions in dogs.
- Selected subaortic or pulmonic stenosis cases, hypertension and ferret hypertrophic cardiomyopathy.
Contraindications
- Clinically significant bradycardia, advanced AV block or cardiogenic shock.
- Initiation or escalation during decompensated heart failure requires particular caution.
- Use cautiously with bronchospastic airway disease and renal dysfunction.
- Not suitable as sole therapy for feline primary systemic hypertension.
- In labile diabetes, beta blockade may mask warning signs of hypoglycemia and alter glycemic control.
Interactions
- Amiodarone, digoxin and calcium-channel blockers may add to bradycardia or AV block.
- Other negative inotropes may worsen cardiac output.
- Reserpine and other antihypertensives can add hypotension or bradycardia. Sympathomimetic bronchodilators and atenolol may oppose each other.
Adverse effects
- Bradycardia, hypotension and AV block.
- Weakness or worsening heart failure.
- Bronchospasm in susceptible patients.
- Syncope, diarrhea and altered glucose regulation may occur.
Toxicity
Monitor heart rate, rhythm, blood pressure and signs of congestion. Severe overdose can cause low-output shock; taper sustained therapy rather than stopping abruptly.
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 |
