How does this medication work? What will it do for me?

Atenolol belongs to a class of medications called beta-blockers. It is used to lower high blood pressure and to prevent the symptoms of angina (chest pain). It works by reducing the demands put on the heart.

Atenolol is often used in combination with other high blood pressure medications such as diuretics (water pills) when the use of one medication by itself is not enough to control blood pressure.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

This medication is available as 50 mg and 100 mg tablets.

How should I use this medication?

The recommended adult dose of atenolol ranges from 50 mg to 100 mg once daily depending on circumstances. If you have reduced kidney function you may need much lower doses. The full effect of the medication is usually reached within 1 to 2 weeks. If blood pressure is not reduced sufficiently after this time, your doctor may increase the dose of the medication or add another blood pressure-lowering medication. If satisfactory results are not seen within 1 week for treatment of angina, your doctor may increase the dose of atenolol.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to atenolol or any ingredients of the medication
  • have a condition known as pheochromocytoma (in the absence of alpha-blockade)
  • have a condition known as right ventricular failure caused by pulmonary hypertension
  • have a condition known as "sick sinus syndrome"
  • have a very slow heart rate
  • have congestive heart failure
  • have metabolic acidosis
  • have serious heart block (second- or third-degree AV block)
  • have severe peripheral arterial disorders (blockage of blood flow to limbs of body)
  • have very low blood pressure

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • diarrhea
  • dizziness or lightheadedness
  • dry mouth
  • nausea
  • unusual tiredness or weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • back pain or joint pain
  • breathing difficulty or wheezing
  • cold hands and feet
  • confusion (especially in seniors)
  • depression
  • dizziness or lightheadedness when getting up from a lying or sitting position
  • fever and sore throat
  • hallucinations
  • swelling of ankles, feet, or lower legs
  • symptoms of liver damage (such as yellow skin or eyes, abdominal pain, dark urine, clay-coloured stools, loss of appetite, nausea and vomiting, or itching)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • chest pain
  • irregular heartbeat
  • lightheadedness or passing out
  • red, scaling, or crusted skin
  • signs of an allergic reaction (such as difficulty breathing, hives, swelling of the face or throat)
  • signs of bleeding (such as easy bruising, bleeding gums, nosebleeds, vomiting blood, blood in the urine, dark tarry stools)
  • severe shortness of breath
  • severely slow heartbeat (especially less than 50 beats per minute)
  • swelling of the hands or feet with shortness of breath
  • symptoms of a serious allergic reaction (such as swelling of the face or throat, hives, or difficulty breathing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Breathing conditions: In general, people who have asthma and certain other breathing problems or chronic lung disease should not take a beta-blocker such as atenolol. Low doses of atenolol may be taken with caution by those with asthma who do not respond to or cannot tolerate alternative treatment.

Drowsiness/reduced alertness: The use of atenolol is unlikely to impair your ability to drive or operate machinery. However, it should be taken into account that dizziness, fatigue, or a slower reaction time may occur.

History of heart failure: If you have a history of heart failure you should be cautious while taking atenolol as it may increase the risks associated with this condition.

Hyperthyroidism:If you have hyperthyroidism (high levels of thyroid hormones) you should use caution while taking atenolol as it may reduce the symptoms of this condition, giving a false impression of improvement. Stopping the medication suddenly could worsen this condition.

Kidney disease: If you have kidney disease you should use caution while taking atenolol as you are at increased risk of experiencing side effects.

Low blood sugar: The signs of low blood sugar may not be as noticeable when taking atenolol. If you have diabetes and take insulin or other medications that affect insulin levels in the blood, you should be cautious and monitor blood sugar carefully while taking this medication.

Prinzmetal's angina: Atenolol may increase the number and duration of angina attacks in patients with Prinzmetal's angina. Therefore, people who have this condition should be cautious while taking atenolol.

Severe allergies: If you have allergies severe enough to cause anaphylaxis (a severe allergic reaction where swelling of the face, lips, and throat make it difficult to breathe), you should talk to your doctor about what to do if you have an allergic reaction. Atenolol may make it more difficult to treat your allergic reaction with epinephrine.

Slow heart rate: In general, people with an abnormally slow pulse should not take a beta-blocker such as atenolol.

Stopping usage: Atenolol should not be stopped suddenly. There have been reports of severe worsening of angina and of heart attack or abnormal heart rhythms occurring in people with angina pectoris who have done this.

Surgery: If you are scheduled for surgery, inform all doctors involved in your care that you are taking atenolol.

Pregnancy: There have not been adequate studies on the use of atenolol by pregnant women; however, studies have shown that atenolol does cross the placenta. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking atenolol, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

What other drugs could interact with this medication?

There may be an interaction between atenolol and any of the following:

  • amiodarone
  • amlodipine
  • anesthetic agents
  • antidiabetes medication (e.g., insulin)
  • clonidine
  • digoxin
  • diltiazem
  • disopyramide
  • felodipine
  • flecainide
  • guanethidine
  • mexiletene
  • nifedipine
  • nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., ibuprofen)
  • procainamide
  • propafenone
  • quinidine
  • reserpine
  • verapamil

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.