Atenolol

What is this medication for?

• Supraventricular tachyarrhythmias, subaortic/pulmonic stenosis, high blood pressure
• Hypertrophic cardiomyopathy (rate control), hyperthyroid-associated unusually fast heart rate/high blood pressure

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Do not stop abruptly — withdraw gradually to avoid rebound exacerbation of underlying cardiac disease (extrapolated from human data).

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Lethargy, low blood pressure (Can occur within 1h of dosing)
• Bradycardia, impaired AV conduction (Expected pharmacologic effect)
• Diarrhea, syncope (Reported)
• Bronchoconstriction (Less likely than non-selective beta-blockers, but possible at higher doses)

Worth a phone call to your veterinarian

• Any new symptom that worries you.

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Overt heart failure (unless 2° to tachyarrhythmia), >1st-degree heart block, sinus unusually slow heart rate, hypersensitivity
• has or has had: May mask hypoglycemia/hyperthyroidism signs; bronchospastic disease (relatively safer than non-selective beta-blockers); renal insufficiency, sinus node dysfunction; labile diabetics

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Calcium channel blockers (diltiazem, verapamil)
  • Furosemide, other hypotensive agents
  • Sympathomimetics (terbutaline, epinephrine's beta effects)
  • Clonidine

Storage and handling

Room temperature, protect from heat/light/moisture. Compounded suspensions: avoid sugar-containing vehicles (reduces potency); stable ~90 days in Ora-Plus/Ora-Sweet SF.

Good to know

• Do not stop abruptly — withdraw gradually to avoid rebound exacerbation of underlying cardiac disease (extrapolated from human data).
• Comparatively safe in patients with bronchospastic disease due to beta-1 selectivity at usual doses, but selectivity is lost at higher doses.
• May reduce clinical signs in cats with HCM but has not been shown to slow disease progression.