What is Tenormin

Tenormin is a brand name of a second generation cardioselective beta-blocker called atenolol, that is used in the treatment of hypertension (high blood pressure), angina pectoris (heart chest pain) and acute myocardial infarction (heart attack). Tenormin is also used to lower the risk of death after a heart attack. Non-FDA approved indications include treatment of arrhythmias (irregular heartbeat), migraine prophylaxis, paroxysmal supraventricular tachycardia, alcohol withdrawal, thyrotoxicosis and prophylaxis against secondary myocardial infarction 1). Tenormin (atenolol) works by relaxing blood vessels and slowing heart rate to improve blood flow and decrease blood pressure.

Tenormin (atenolol) was approved for use in the United States in 1981 and is still widely used in the therapy of hypertension and angina pectoris. Tenormin (atenolol) is also used to reduce the risk of cardiovascular mortality in patients with coronary artery disease.

Tenormin (atenolol) is considered a “selective” beta-adrenergic receptor blocker in that it has potent activity against beta-1 adrenergic receptors which are found in cardiac muscle, but has little or no activity against beta-2 adrenergic receptors found on bronchial and vascular smooth muscle.

Tenormin (atenolol) is available in 25, 50 and 100 mg tablets in generic forms as well as under the trade name of Tenormin. It is also available in fixed combinations with a diuretic such as chlorthalidone (Tenoretic and others). Parenteral formulations for intravenous use are also available. The usual oral dose of tenormin (atenolol) in adults is 25 to 50 mg once daily initially, with subsequent adjustment based upon clinical response and tolerance, but rarely beyond 100 mg daily.

Tenormin (atenolol) controls high blood pressure and angina but does not cure them. It may take 1-2 weeks before you feel the full benefit of tenormin (atenolol). Continue to take tenormin (atenolol) even if you feel well. Do not stop taking tenormin (atenolol) without talking to your doctor.

Tenormin (atenolol) common side effects include bradycardia, hypotension, fatigue, dizziness, depression, memory loss and impotence. At high doses, tenormin (atenolol) is less cardioselective and can cause bronchospasm. As with all beta-blockers, sudden withdrawal can trigger rebound hypertension.


Do not stop taking Tenormin (atenolol) without talking to your doctor. Suddenly stopping Tenormin (atenolol) may cause chest pain, heart attack, or irregular heartbeat. Your doctor will probably decrease your dose gradually.

Tenormin mechanism of action

Cardioselective beta-1-adrenergic antagonists such as Tenormin (atenolol) work by selectively binding to the beta-1 adrenergic receptors found in vascular smooth muscle and the heart, blocking the positive inotropic and chronotropic actions of endogenous catecholamines such as isoproterenol, norepinephrine, and epinephrine, thereby inhibiting sympathetic stimulation 2). This activity results in a reduction in heart rate, blood pressure and decreased myocardial contractility. However, in heart failure patients, Tenormin (atenolol) can increase the end diastolic pressure and left ventricular fiber lengths – conversely resulting in increased oxygen demand. In higher doses, it also exerts its effects by competitively blocking beta-2-adrenoreceptors primarily located in the bronchial and vascular musculature. Due to lack of membrane stabilizing or intrinsic sympathomimetic activity, Tenormin (atenolol) has low lipid solubility, and reduced brain penetrance is thereby resulting in fewer CNS (central nervous system) side effects 3). B-adrenoreceptor antagonists are also known to increase the AV node’s refractory period. Therefore it may also be used off-license for the treatment of supraventricular tachycardia, and the prevention of paroxysmal attacks of atrial fibrillation 4). The duration of action is dose related – following administration of a dose, the effects are apparent within an hour and are maximal at 2 to 4 hours, persisting for at least 24 hours.

What is tenormin used for?

Tenormin (atenolol) is used alone or in combination with other medications to treat high blood pressure. Tenormin (atenolol) also is used to prevent angina (chest pain) and improve survival after a heart attack. High blood pressure is a common condition and when not treated, can cause damage to the brain, heart, blood vessels, kidneys and other parts of the body. Damage to these organs may cause heart disease, a heart attack, heart failure, stroke, kidney failure, loss of vision, and other problems. In addition to taking medication, making lifestyle changes will also help to control your blood pressure. These changes include eating a diet that is low in fat and salt, maintaining a healthy weight, exercising at least 30 minutes most days, not smoking, and using alcohol in moderation.

Non-FDA approved indications include treatment of arrhythmias, migraine prophylaxis, paroxysmal supraventricular tachycardia, alcohol withdrawal, thyrotoxicosis and prophylaxis against secondary myocardial infarction 5).

Tenormin special precautions

Before taking Tenormin (atenolol):

  • tell your doctor and pharmacist if you are allergic to atenolol, any other medications, or any of the ingredients in atenolol tablets. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking. Be sure to mention any of the following: calcium channel blockers such as diltiazem (Cardizem, Cartia XT, Dilacor XR, Tiazac, others) and verapamil (Calan, Covera-HS, Verelan, in Tarka); clonidine (Catapres, Kapvay, in Clorpres); nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin (Indocin, Tivorbex); and reserpine. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
    tell your doctor if you have or have ever had asthma or other lung diseases; diabetes; severe allergies; hyperthyroidism (an overactive thyroid gland); pheochromocytoma (a tumor that develops on a gland near the kidneys and may cause high blood pressure and fast heartbeat); heart failure; a slow heart rate; circulation problems; or heart or kidney disease.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking atenolol, call your doctor immediately.
  • if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking atenolol.
  • you should know that if you have allergic reactions to different substances, your reactions may be worse while you are using atenolol, and your allergic reactions may not respond to the usual doses of injectable epinephrine.
  • The use of Tenormin (atenolol) is not recommended in children as even small amounts can result in an overdose.

Special dietary instructions

If your doctor prescribes a low-salt or low-sodium diet, follow these directions carefully.


Contraindications to Tenormin (atenolol) include sinus bradycardia, second or third-degree heart block, cardiogenic shock, heart failure, severe peripheral arterial disease, metabolic acidosis, and pheochromocytoma 6). It should also be avoided in patients with a history of asthma, bronchospasm or other obstructive airway diseases unless there is no alternative, in which case it may be given alongside a bronchodilator 7).

Caution is necessary when prescribing to diabetic or thyroid patients as its effects may mask the symptoms of hypoglycemia and thyrotoxicosis – rapid withdrawal may also precipitate a thyroid storm. Prescribers should exercise caution during pregnancy – Tenormin (atenolol) has been shown to cross the placental barrier and is associated with intrauterine growth restriction. Use during breastfeeding is recommended against by the American Academy of Pediatrics due to a risk of neonatal hypoglycemia and bradycardia 8).


Pregnancy Category D: Studies in pregnant women have demonstrated a risk to the fetus. However, the benefits of therapy in a life threatening situation or a serious disease, may outweigh the potential risk.


There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking Tenormin (atenolol), it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using Tenormin (atenolol) with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Ceritinib
  • Clonidine
  • Crizotinib
  • Diltiazem
  • Dronedarone
  • Fenoldopam
  • Fingolimod
  • Iohexol
  • Lacosamide
  • Rivastigmine
  • Siponimod
  • Verapamil

Using Tenormin (atenolol) with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Acarbose
  • Aceclofenac
  • Acemetacin
  • Acetyldigoxin
  • Albiglutide
  • Alfuzosin
  • Alogliptin
  • Amtolmetin Guacil
  • Arbutamine
  • Aspirin
  • Bromfenac
  • Bufexamac
  • Bunazosin
  • Canagliflozin
  • Celecoxib
  • Chlorpropamide
  • Choline Salicylate
  • Clonixin
  • Dapagliflozin
  • Deslanoside
  • Dexibuprofen
  • Dexketoprofen
  • Diclofenac
  • Diflunisal
  • Digitoxin
  • Digoxin
  • Dipyrone
  • Disopyramide
  • Doxazosin
  • Droxicam
  • Dulaglutide
  • Empagliflozin
  • Ertugliflozin
  • Etodolac
  • Etofenamate
  • Etoricoxib
  • Exenatide
  • Felbinac
  • Fenoprofen
  • Fepradinol
  • Feprazone
  • Floctafenine
  • Flufenamic Acid
  • Flurbiprofen
  • Glimepiride
  • Glipizide
  • Glyburide
  • Ibuprofen
  • Indomethacin
  • Insulin Aspart, Recombinant
  • Insulin Degludec
  • Insulin Detemir
  • Insulin Glargine, Recombinant
  • Insulin Glulisine
  • Insulin Human Inhaled
  • Insulin Human Isophane (NPH)
  • Insulin Human Regular
  • Insulin Lispro, Recombinant
  • Ketoprofen
  • Ketorolac
  • Linagliptin
  • Liraglutide
  • Lixisenatide
  • Lornoxicam
  • Loxoprofen
  • Lumiracoxib
  • Meclofenamate
  • Mefenamic Acid
  • Meloxicam
  • Metformin
  • Metildigoxin
  • Mibefradil
  • Miglitol
  • Morniflumate
  • Moxisylyte
  • Nabumetone
  • Naproxen
  • Nateglinide
  • Nepafenac
  • Niflumic Acid
  • Nimesulide
  • Nimesulide Beta Cyclodextrin
  • Oxaprozin
  • Oxyphenbutazone
  • Parecoxib
  • Phenoxybenzamine
  • Phentolamine
  • Phenylbutazone
  • Piketoprofen
  • Pioglitazone
  • Piroxicam
  • Pramlintide
  • Pranoprofen
  • Prazosin
  • Proglumetacin
  • Propyphenazone
  • Proquazone
  • Quinidine
  • Repaglinide
  • Rofecoxib
  • Rosiglitazone
  • Salicylic Acid
  • Salsalate
  • Saxagliptin
  • Sitagliptin
  • Sodium Salicylate
  • St John’s Wort
  • Sulindac
  • Tamsulosin
  • Tenoxicam
  • Terazosin
  • Tiaprofenic Acid
  • Tolazamide
  • Tolbutamide
  • Tolfenamic Acid
  • Tolmetin
  • Trimazosin
  • Urapidil
  • Valdecoxib
  • Vildagliptin

Other interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other medical problems

The presence of other medical problems may affect the use of Tenormin (atenolol). Make sure you tell your doctor if you have any other medical problems, especially:

  • Bradycardia (slow heartbeat) or
  • Heart block or
  • Heart failure or
  • Pheochromocytoma (adrenal gland tumor), untreated—Should not use in patients with these conditions .
  • Diabetes or
  • Hyperthyroidism (overactive thyroid) or
  • Hypoglycemia (low blood sugar)—May cover up some of the signs and symptoms of these diseases, such as a fast heartbeat .
  • Kidney disease—Use with caution. The effects may be increased because of slower removal from the body .
  • Lung disease (e.g., asthma, bronchitis, emphysema)—May cause difficulty with breathing in patients with this condition .

Tenormin dosage

The dose of Tenormin (atenolol) will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of Tenormin (atenolol). If your dose is different, do not change it unless your doctor tells you to do so.

The amount of Tenormin (atenolol) that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For oral dosage form (tablets):

  • For acute heart attack:
    • Adults—50 milligrams (mg) ten minutes after the last intravenous (IV) dose followed by another 50 mg twelve hours later. Then, 100 mg once a day or 50 mg two times a day for another 6 to 9 days or until discharge from the hospital.
    • Children—Use and dose must be determined by your doctor .
  • For chest pain:
    • Adults—At first, 50 milligrams (mg) once a day. Your doctor may increase your dose if needed.
    • Children—Use and dose must be determined by your doctor .
  • For high blood pressure:
    • Adults—At first, 50 milligrams (mg) once a day. Your doctor may increase your dose if needed.
    • Children—Use and dose must be determined by your doctor .


The initial adult dose of atenolol is 50 mg per day given either as a single table or in conjunction with diuretic therapy. In the absence of an adequate therapeutic response after a few weeks, the dosage may be increased to a single 100mg tablet once a day. Daily doses higher than this are unlikely to produce further benefit. For renal-impaired or elderly patients, a lower dose of 25mg once a day may be used if they have a creatinine clearance of under 15 ml/min or a maximum dose of 50mg a day if the creatinine clearance is 15 to 35 ml/min. Careful monitoring of their blood pressure prior to administering a new dose is necessary.

Angina Pectoris

The initial adult dose is 50 mg tablet once a day. If after a week optimal response has not been reached, the dose should be increased to one 100mg tablet daily. Some patients may need 200mg daily for an optimal therapeutic response. However, withdrawal should be achieved gradually with the patient monitored and advised to limit physical activity during this time.

Acute Myocardial Infarction

Intravenous injection should be initiated as soon as possible after the patient’s arrival in the hospital, within 12 hours of the myocardial infarction. The FDA recommends for an adult, the IV administration of 5mg of atenolol over 5 minutes followed by another 5mg IV injection after 10 minutes. A 50mg oral dose should follow 12 hours later. After that, oral dosing can be either 50mg twice a day or 100mg once a day for 6 to 9 days or until discharged from the hospital.

What should I do if I forget a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Tenormin side effects

Tenormin (atenolol) common side effects include:

  • bronchospasm
  • bradycardia
  • diarrhea
  • dizziness
  • constipation
  • confusion
  • dyspnea
  • headache
  • heart failure
  • erectile dysfunction
  • nausea
  • fatigue
  • paresthesia
  • peripheral coldness
  • rash
  • sleep disorders
  • syncope
  • visual impairment
  • vomiting.

Rare side effects include:

  • alopecia
  • dry mouth
  • hepatic disorders
  • depression
  • postural hypotension
  • psychosis
  • skin reactions
  • thrombocytopenia.

Tenormin (atenolol) may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • dizziness
  • lightheadedness
  • tiredness
  • drowsiness
  • depression
  • nausea
  • diarrhea

Some side effects can be serious. The following symptoms are uncommon, but if you experience any of them, call your doctor immediately:

  • shortness of breath
  • swelling of the hands, feet, ankles, or lower legs
  • weight gain
  • fainting

Tenormin (atenolol) may cause other side effects. Call your doctor if you have any unusual problems while taking Tenormin (atenolol).

Symptoms of Tenormin (atenolol) overdose may include:

  • lack of energy
  • difficulty breathing
  • wheezing
  • slow heartbeat
  • fainting
  • swelling of the hands, feet, ankles, or lower legs
  • unusual weight gain
  • shakiness
  • dizziness
  • rapid heartbeat
  • sweating or confusion
  • blurred vision
  • headache
  • numbness or tingling of the mouth
  • weakness
  • excessive tiredness
  • pale color
  • sudden hunger

The use of inotropes and chronotropes such as intravenous epinephrine and atropine is a recommended measure for the treatment of severe bradycardia. Usually, atropine is administered as a 0.5 mg IV or IO bolus and repeated the every 3 to 5 minutes to a total dose of 3 mg. A transvenous cardiac pacemaker may be used in refractory cases, or for the treatment of second or third-degree heart block. A titred bolus of glucagon at a dose of 50 mcg/kg can improve myocardial contractility, atrioventricular conduction and increase heart rate in patients. Blood pressure must undergo continuous monitoring, and in cases of hypotension, vasopressors such as levarterenol are an option. For patients with bronchospasm, a beta-2 agonist such as aminophylline or isoproterenol may be used to alleviate symptoms. In cases that are refractory to the usual treatment, high dose insulin at 1 unit/kg bolus followed by 1 unit/kg per hour drip may be used to treat overdose in consultation with a toxicologist 9).

In cases of asymptomatic, beta-1-blocker overdoses, the recommendation is to monitor the patient for at least 6 hours 10).

References   [ + ]

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