Do not stop taking this medication without consulting your doctor. Some conditions may become worse when you suddenly stop this drug. Some people who have suddenly stopped taking similar drugs have had chest pain, heart attack, and irregular heartbeat. If your doctor decides you should no longer use this drug, he or she may direct you to gradually decrease your dose over 1 to 2 weeks.

When gradually stopping this medication, it is recommended that you temporarily limit physical activity to decrease strain on the heart. Seek immediate medical attention if you develop chest pain/tightness/pressure, chest pain spreading to the jaw/neck/arm, unusual sweating, trouble breathing, or fast/irregular heartbeat.

This medication is used to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. This product contains 2 medications, atenolol and chlorthalidone. Atenolol belongs to a class of drugs known as beta blockers. It works by keeping certain natural chemicals such as epinephrine from acting on the heart and blood vessels. This effect lowers the heart rate, blood pressure, and strain on the heart. Chlorthalidone is a "water pill" (diuretic) and causes your body to get rid of extra salt and water. This effect may increase the amount of urine you make when you first start the medication. It also helps to relax the blood vessels so that blood can flow more easily.

See also Warning section.

Take this medication by mouth with or without food, usually once daily or as directed by your doctor.

If you take this drug too close to bedtime, you may need to wake up to urinate. Therefore, it is best to take this medication at least 4 hours before your bedtime. Consult your doctor or pharmacist if you have questions about when to take this medication.

The dosage is based on your medical condition and response to treatment.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.

It may take several weeks before you get the full benefit of this medication. It is important to continue taking this medication even if you feel well. Most people with high blood pressure do not feel sick.

Tell your doctor if your condition does not improve or if it worsens (for example, your routine blood pressure readings remain high or increase).

See also Warning and Precautions sections.

Dizziness, lightheadedness, slow heartbeat, tiredness, nausea, and diarrhea may occur. Decreased sexual ability has been reported infrequently. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

To lower your risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

This product may reduce blood flow to your hands and feet, causing them to feel cold. Smoking may worsen this effect. Dress warmly and avoid tobacco use.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

The chlorthalidone in this product may cause your body to lose too much water and salt (dehydration). Tell your doctor immediately if you have any of these unlikely but serious symptoms of dehydration: very dry mouth, extreme thirst, muscle cramps/weakness, fast heartbeat, severe dizziness, confusion, fainting, seizures.

Tell your doctor immediately if any of these unlikely but serious side effects occur: very slow/irregular heartbeat, new or worsening symptoms of heart failure (such as swelling ankles/feet, severe tiredness, shortness of breath, unexplained/sudden weight gain), mental/mood changes (such as depression, mood swings), toe/joint pain.

Tell your doctor immediately if any of these rare but very serious side effects occur: trouble breathing, blue fingers/toes, easy bruising/bleeding, signs of infection (such as fever, persistent sore throat), yellowing eyes/skin, persistent nausea/vomiting, severe stomach/abdominal pain, dark urine, change in the amount of urine (not including the normal increase in urine when you first start this drug).

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking this product, tell your doctor or pharmacist if you are allergic to atenolol or chlorthalidone; or to thiazide diuretics (such as hydrochlorothiazide); or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: certain types of heart rhythm problems (such as a slow heartbeat, second- or third-degree atrioventricular block, sick sinus syndrome), an inability to make urine (anuria).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: blood circulation problems (such as Raynaud's disease, peripheral vascular disease), pheochromocytoma, liver disease, kidney disease, heart failure, overactive thyroid (hyperthyroidism), gout, untreated salt imbalance (for example, high calcium, low potassium, low magnesium), loss of too much body water (dehydration), a certain muscle/nerve disease (myasthenia gravis), lupus, breathing problems (such as asthma, chronic bronchitis, emphysema), serious allergic reactions including those needing treatment with epinephrine, mental/mood disorders (such as depression).

Before having surgery, tell your doctor or dentist that you are taking this medication.

This drug may make you dizzy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages.

To help prevent dizziness, drink plenty of fluids while taking this medication unless your doctor directs you otherwise. Too much sweating, diarrhea, or vomiting may cause you to feel lightheaded. Report prolonged diarrhea or vomiting to your doctor.

This medication may reduce the potassium levels in your blood. Ask your doctor about adding potassium to your diet. Your doctor may prescribe a potassium supplement.

If you have diabetes, this product may prevent the fast/pounding heartbeat you would usually feel when your blood sugar level falls too low (hypoglycemia). Other symptoms of a low blood sugar level, such as dizziness and sweating, are unaffected by this drug. This product may also make it harder to control your blood sugar levels. Check your blood sugar levels regularly as directed by your doctor. Tell your doctor immediately if you have symptoms of high blood sugar such as increased thirst/urination. Your diabetes medication or diet may need to be adjusted.

This medication may make you more sensitive to the sun. Avoid prolonged sun exposure, tanning booths, and sunlamps. Use a sunscreen and wear protective clothing when outdoors.

Older adults may be more sensitive to the side effects of this drug, including dizziness.

During pregnancy, this medication should be used only when clearly needed. It may harm an unborn baby. Discuss the risks and benefits with your doctor.

Atenolol and chlorthalidone pass into breast milk. Atenolol may have undesirable effects on a nursing infant. Discuss the risks and benefits with your doctor before breast-feeding.

See also Precautions section.

Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.

This drug should not be used with the following medication because very serious interactions may occur: cisapride.

If you are currently using this medication, tell your doctor or pharmacist before starting this product.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: lithium, drugs that lower your potassium level (including corticosteroids such as prednisone), mefloquine.

Cholestyramine and colestipol can decrease the absorption of hydrochlorothiazide. If you are taking either of these drugs, take them at least 4 hours before or after taking this product.

Check the labels on all your medicines (such as cough-and-cold products, diet aids, nonsteroidal anti-inflammatory drugs-NSAIDs such as ibuprofen for pain/fever reduction) because they may contain ingredients that could increase your blood pressure or heart rate. Ask your pharmacist about using those products safely.

If your doctor has directed you to take low-dose aspirin for heart attack or stroke prevention (usually at dosages of 81-325 milligrams a day), you should continue taking it unless your doctor instructs you otherwise. Ask your doctor or pharmacist for more details.

This product may interfere with certain laboratory tests (including parathyroid, protein-bound iodide, tyramine, and phentolamine tests), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US National Poison Hotline at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe dizziness, fainting, very slow heartbeat, trouble breathing.

Do not share this medication with others.

Talk with your doctor about making changes to your lifestyle that may help this medication work better (such as stress reduction programs, exercise, and dietary changes).

Laboratory and/or medical tests (including kidney/liver function tests, blood mineral levels such as potassium) should be performed regularly to monitor your progress or check for side effects. Consult your doctor for more details.

Have your blood pressure and heart rate checked regularly while taking this medication. Learn how to check your own blood pressure and heart rate at home, and share the results with your doctor.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

Store at room temperature between 68-77 degrees F (20-25 degrees C) away from light and moisture. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

MEDICAL ALERT: Your condition can cause complications in a medical emergency. For enrollment information call MedicAlert at 1-800-854-1166 (USA) or 1-800-668-1507 (Canada).

Information last revised July 2009 Copyright(c) 2009 First DataBank, Inc.