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 Tenormin (Atenolol). If you are concerned about side effects, discuss the risks and benefits of Tenormin (Atenolol) with your doctor.

The following side effects have been reported by at least 1% of people taking Tenormin (Atenolol). 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.

• back or joint pain
• Constipation
• cough
• decreased interest or ability for sexual activity
• Diarrhea
• dizziness or lightheadedness
• Dry Mouth
• headache
• nausea
• slow heart rate
• spinning sensation
• trouble sleeping
• 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:

• breathing difficulty or wheezing
• cold hands and feet
• confusion (especially in seniors) or memory problems
• dizziness or lightheadedness when getting up from a lying or sitting position
• irregular heartbeat or palpitations
• signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
• skin rash
• vision problems
• worsening heart failure (e.g., swelling of ankles, feet, or lower legs, difficulty breathing)

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

• chest pain
• severe shortness of breath
• severely slow heartbeat (especially less than 50 beats per minute)
• 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 Tenormin (Atenolol).

50 mg
Each scored, white-to-off-white, biconvex, film-coated tablet, embossed with "TENORMIN 50" on one side and scored on the other side, contains 50 mg of Tenormin (Atenolol). Nonmedicinal ingredients: gelatin, glycerol, heavy magnesium carbonate, hydroxypropyl methylcellulose, magnesium stearate, maize starch, sodium lauryl sulfate, and titanium dioxide.

100 mg
Each scored, white-to-off-white, biconvex, film-coated tablet, embossed with "TENORMIN" on one side and scored on the other side, contains 100 mg of Tenormin (Atenolol). Nonmedicinal ingredients: gelatin, glycerol, heavy magnesium carbonate, hydroxypropyl methylcellulose, magnesium stearate, maize starch, sodium lauryl sulfate, and titanium dioxide.

Do not take Tenormin (Atenolol) if you:

• are allergic to Tenormin (Atenolol) or any ingredients of the medication
• are allergic to other beta-blockers
• are scheduled to have anesthesia with an agent that causes myocardial Depression (e.g., ether)
• 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 caused by heart rhythm problems
• have Congestive Heart Failure
• have metabolic acidosis
• have cardiogenic shock
• 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

There may be an interaction between Tenormin (Atenolol) and any of the following:

• Aldesleukin
• Aliskiren
• alpha-agonists (e.g., Clonidine, methyldopa)
• alpha-blockers (e.g., Alfuzosin, Doxazosin, Tamsulosin)
• amifostine
• Amiodarone
• amphetamines (e.g., Dextroamphetamine, Lisdexamfetamine)
• ampicillin
• anesthetic agents
• angiotensin converting enzyme inhibitors (ACEIs; Captopril, Ramipril)
• angiotensin receptor blockers (ARBs; e.g., Candesartan, Irbesartan, Losartan)
• barbiturates (e.g., butalbital, pentobarbital, Phenobarbital)
• beta-2 agonists (e.g., salbutamol, formoterol, terbutaline)
• beta-adrenergic blockers (e.g., Tenormin (Atenolol), Propranolol, Sotalol)
• brimonidine
• bupivacaine
• caffeine
• calcium channel blockers (e.g., Amlodipine, Diltiazem, Nifedipine, Verapamil)
• Ceritinib
• decongestant medications (e.g., phenylephrine, Pseudoephedrine)
• dexmethylphenidate
• Digoxin
• Dipyridamole
• Disopyramide
• diuretics (water pills; e.g., Furosemide, Hydrochlorothiazide, triamterene)
• Donepezil
• Dronedarone
• Duloxetine
• epinephrine
• ergot alkaloids (e.g., Dihydroergotamine, ergonovine,  ergotamine, methylergonovine)
• Fentanyl
• Fingolimod
• Flecainide
• Galantamine
• glycopyrrolate
• grass pollen allergen extract
• Guanfacine
• insulin
• Ivabradine
• Lacosamide
• Lanreotide
• levodopa
• lidocaine
• Mefloquine
• Methylphenidate
• Mexiletine
• Minoxidil
• narcotic pain relievers (e.g., Codeine, fentanyl, Morphine, Oxycodone)
• nitrates (e.g., Nitroglycerin, isosorbide dinitrate, isosorbide mononitrate)
• nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., Ibuprofen, Diclofenac, Ketorolac)
• norephinephrine
• Obinutuzumab
• Octreotide
• Pasireotide
• Pentoxifylline
• phosphodiesterase-5 inhibitors (e.g., Sildenafil, Tadalafil, Vardenafil)
• Pilocarpine
• procainamide
• Propafenone
• quinidine
• quinine
• reserpine
• Rivastigmine
• Ropinirole
• second-generation anti-psychotics (e.g., Clozapine, Olanzapine, Quetiapine, Risperidone)
• Selegiline
• sulfonylureas (e.g., Gliclazide, Glyburide, Tolbutamide)
• theophyllines (e.g., Aminophylline, Oxtriphylline, Theophylline)
• Tizanidine
• Tofacitinib
• tolcapone
• Yohimbine

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 Tenormin (Atenolol). 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.

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 Tenormin (Atenolol).

Breathing conditions: In general, people who have Asthma and certain other breathing problems or chronic lung disease should avoid taking a beta-blocker such as Tenormin (Atenolol), as it can cause breathing difficulty. Low doses of Tenormin (Atenolol) may be taken with caution by people with asthma who do not respond to or cannot tolerate alternative treatment. If you have breathing problems, discuss with your doctor how Tenormin (Atenolol) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Tenormin (Atenolol), and whether any special monitoring is needed.

Drowsiness/reduced alertness: The use of Tenormin (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: Beta-blockers, such as Tenormin (Atenolol), can worsen existing heart failure. It is important to take Tenormin (Atenolol) exactly as prescribed by your doctor to decrease the chance of this happening. If you have a history of heart disease, discuss with your doctor how Tenormin (Atenolol) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Tenormin (Atenolol), and whether any special monitoring is needed.

Hyperthyroidism: If you have hyperthyroidism (high levels of Thyroid hormones) you should use caution while taking Tenormin (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: The kidneys are partially responsible for removing Tenormin (Atenolol) from your body. Kidney disease or reduced kidney function may cause Tenormin (Atenolol) to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how Tenormin (Atenolol) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Tenormin (Atenolol), and whether any special monitoring is needed.

Low blood sugar: The signs of low blood sugar may not be as noticeable when taking Tenormin (Atenolol). If you have Diabetes and take insulin or other medications that affect insulin levels in the blood, discuss with your doctor how Tenormin (Atenolol) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Tenormin (Atenolol), and whether any special monitoring is needed. Your doctor will monitor you while you are taking Tenormin (Atenolol) and may need to adjust the doses of diabetes medications.

Prinzmetal's angina: Tenormin (Atenolol) may increase the number and duration of angina attacks in patients with Prinzmetal's angina. If you have this condition, be cautious while taking Tenormin (Atenolol). Report unusual chest pain to your doctor as soon as possible.

Severe allergies: If you have allergies severe enough to cause Anaphylaxis (severe allergic reaction) (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. Tenormin (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 Tenormin (Atenolol).

Stopping usage: Tenormin (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. If Tenormin (Atenolol) needs to be stopped, it should be done gradually under supervision of your doctor.

Surgery: If you are scheduled for surgery, inform all doctors involved in your care that you are taking Tenormin (Atenolol).

Pregnancy: Studies have shown that Tenormin (Atenolol) does cross the placenta and there have been reports of harm to the developing baby if Tenormin (Atenolol) is taken by the mother during pregnancy. Tenormin (Atenolol) should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Tenormin (Atenolol), contact your doctor immediately.

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

Children: The safety and effectiveness of using Tenormin (Atenolol) have not been established for children.