Take care of your blood pressure with Atenolol (generic Tenormin)

Atenolol (Tenormin) effectively treats hypertension but also can be used to treat angina (chest pain). Its active ingredient is a beta-blocker that widens blood vessels and increases blood flow.

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Written by Dr Kim Langdon, MD

Information last reviewed 06/21/19


What is Atenolol?

Atenolol (Tenormin) is used to lower blood pressure, but it can also be used for other conditions, such as angina. Atenolol is a type of antihypertensive (high blood pressure drug), known as a beta-blocker. This means that it works by relaxing and widening the blood vessels, this improves the blood flow and reduces your blood pressure.

What is Atenolol used for?

Atenolol is one of the beta-blockers available to treat high blood pressure and coronary artery disease.

How does Atenolol work?

Atenolol works as a beta-blocker, meaning that it blocks the beta receptors on the blood vessels which causes the blood vessels to dilate, therefore reducing blood pressure.

How long does Atenolol take to work?

Atenolol starts to work about 1 hour after taking it. The peak effect is between 2 to 4 hours, the effects can last between 12 to 24 hours.  

How effective is Atenolol?

Atenolol can be effective in reducing blood pressure. It is not the first line treatment. Sometimes, doctors may prescribe Atenolol not only for the blood pressure effect, but also for cardiac (heart) effect in people with coronary artery disease. 


Active ingredients

The active ingredient in Atenolol is atenolol, a type of beta-blocker. Beta-blockers work by blocking the body’s response to adrenaline. Adrenaline normally results in the constriction (narrowing) of the blood vessels, so by blocking this mechanism, the blood vessels are better able to relax and widen, reducing your blood pressure and improving blood flow around the body.

Atenolol blocks the response to beta-adrenergic stimulation. This type of stimulation results in the constriction of blood vessels.  It selectively blocks beta1-receptors with little effect on beta2-receptors. Black Box Warning: Do not stop abruptly.

Inactive ingredients

In addition to Atenolol, the inactive ingredients are: 
Magnesium stearate, maize starch, sodium lauryl sulphate, colloidal anhydrous silica, sodium starch glycollate, magnesium carbonate, hypromellose, macrogol 6000, titanium dioxide, purified talc

Which ingredients can cause an allergic reaction?

Atenolol only causes a severe allergic reaction in rare cases. Unless you are specifically allergic to any of the active or inactive ingredients in atenolol, the drug should be safe for you. If it is your first time taking atenolol, look out for these signs of a severe allergic reaction: hives, difficulty breathing, swelling of the lips/face and dizziness. If you experience any of these please get medical help as soon as possible.


Atenolol dosage

The correct dosage of Atenolol can vary from person to person, but it also depends upon which condition is being treated.

  • To treat high blood pressure (antihypertension), 50mg tablets of Atenolol are given initially. A doctor may review the patient every 1-2 weeks and reduce or increase the dose up to 100mg a day, to make sure the individual patient gets the best treatment for their condition.
  • To treat Angina (chest pain), initially one 50mg tablet is taken once a day. If this doesn’t resolve the problem, the dose may increase up to 200mg daily.
  • Atenolol can also be used as an off-label treatment for atrial fibrillation (AF). AF is when you experience problems controlling your heart rate. Usually 25-100mg is taken once a day to help control AF. (AHA/ACC/HRS [January 2014])

Which strengths of Atenolol are available?

As an oral tablet, Atenolol is available in 25mg, 50mg and 100mg strength tablets. If you require a stronger dose, your doctor may tell you to take more than one tablet a day.

How to take Atenolol

Atenolol can be taken with or without food, and is typically taken once a day.

What should I do if I miss a dose of Atenolol?

If you are within 12 hours of the time your dose would be due, take the missed dose.  However if more than 12 hours have gone by and it is almost time for your next dose, just take the next dose and do not double up the dose that you missed.

Side Effects

Atenolol side effects

Common side effects, affecting more than 10% of people are:

  • Cardiovascular side effects: Hypotension, acute myocardial infarction, cardiac failure, lowered pulse,  elevated pulse, feeling cold
  • Central nervous system side effects: Fatigue, dizziness, depression

Uncommon side effects, affecting between 1-10% of people are:

  • Cardiovascular side effects: Bundle branch block (issues in the electrical signaling around your heart), atrial fibrillation (altered heart rate), heart block (slow heart beat), atrial flutter (abnormal heart rhythm), pulmonary embolism (clot on the lungs)
  • Central nervous system side effects: Abnormal dreams, lethargy, vertigo, drowsiness
  • Gastrointestinal side effects: Nausea, diarrhea
  • Neuromuscular & skeletal side effects: Limb pain
  • Respiratory side effects: Bronchospasm (constriction in the airways)

If you experience any allergic symptoms, including diffculty breathing, you should seek emergency medical attention.

Drug Interactions

Atenolol can interact negatively with a range of other drugs. It is important that you always let the prescribing physician know if you are taking any other medications, especially those with a known Atenolol interaction listed below:

  • Acetylcholinesterase Inhibitors
  • Alfuzosin
  • Alpha1-Blockers
  • Alpha2-Agonists
  • Amifostine
  • Amiodarone
  • Amphetamines
  • Ampicillin
  • Antipsychotic Agents (Second Generation)
  • Bacampicillin
  • Barbiturates
  • Benperidol
  • Beta2-Agonists
  • Bretylium
  • Brigatinib
  • Brimonidine (Topical
  • Bromperidol
  • Calcium Channel Blockers (Nondihydropyridine)
  • Cardiac Glycosides
  • Ceritinib
  • Cholinergic Agonists
  • Dexmethylphenidate
  • Diazoxide
  • Dipyridamole
  • Disopyramide
  • Dronedarone
  • DULoxetine
  • EPINEPHrine (Nasal)
  • EPINEPHrine (Oral Inhalation)
  • EPINEPHrine (Systemic): Beta-Blockers
  • Ergot Derivatives
  • Fingolimod
  • Floctafenine
  • Glycopyrrolate (Systemic)
  • Grass Pollen Allergen Extract (5 Grass Extract)
  • Herbs with hypotensive or hypertensive properties (they may dangerously diminish or increase the effects of Atenolol)
  • Insulins
  • Ivabradine
  • Lacosamide
  • Levodopa
  • Lidocaine (Systemic
  • Lidocaine (Topical
  • Lormetazepam
  • Mepivacaine
  • Methacholine
  • Methoxyflurane
  • Methylphenidate
  • Midodrine
  • Molsidomine
  • Naftopidil
  • Nicergoline
  • Nicorandil
  • Nifedipine
  • Nitroprusside
  • Nonsteroidal Anti-Inflammatory Agents
  • Obinutuzumab
  • Opioids (Anilidopiperidine
  • Pentoxifylline
  • Pholcodine
  • Phosphodiesterase 5 Inhibitors
  • Prostacyclin Analogues
  • Quinagolide
  • Regorafenib
  • Reserpine
  • Rivastigmine
  • Ruxolitinib
  • Siponimod
  • Sulfonylureas
  • Terlipressin
  • Theophylline
  • Tofacitinib
  • Yohimbine


The following conditions are contraindicated for Atenolol:

  • Hypersensitivity to atenolol or any component of the formulation;
  • Sinus bradycardia;
  • Heart block greater than first-degree (except in patients with a functioning artificial pacemaker);
  • Cardiogenic shock;
  • Uncompensated cardiac failure.


You should tell the prescribing physician if you experience any of the following.

  • Bradycardia
  • Low blood pressure

Treatment Options

Atenolol vs. Metoprolol

Atenolol has more blood pressure lowering effects than metoprolol.  Doctors may prescribe metoprolol for other reasons, such as fast heart rates.


Disclaimer: This is not medical advice. You and your physician will determine if and how you should take any medication prescribed to you following a medical consultation.

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