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 blocking the action of certain natural chemicals in your body, such as epinephrine, 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.

These medications are used together when 1 drug alone is not controlling your blood pressure. Your doctor may direct you to start taking the individual medications first, and then switch you over to this combination product if this is the best dose combination for you.

See also Warning section.

Take this medication by mouth with or without food as directed by your doctor, usually once daily. If you take this drug too close to bedtime, you may need to wake up to urinate. It is best to take this medication at least 4 hours before your bedtime. Consult your doctor or pharmacist if you have questions about your dosing schedule.

Apple juice and orange juice may prevent your body from fully absorbing atenolol. It is best to avoid drinking apple/orange juice within 4 hours of taking this medication, unless your doctor or pharmacist tells you otherwise.

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.

If you also take certain drugs to lower your cholesterol (bile acid-binding resins such as cholestyramine or colestipol), take this product at least 2 hours before or at least 4 hours after these medications.

It may take several weeks before you get the full benefit of this medication. Keep 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 get better or if it gets worse (your blood pressure readings remain high or increase).

See also Warning and Precautions sections.

Dizziness, lightheadedness, tiredness, nausea, and diarrhea may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

To reduce the 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 this medication has been prescribed because your doctor 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.

This product may cause dehydration and electrolyte imbalance. Tell your doctor right away if you have any symptoms of dehydration or electrolyte imbalance, including unusual dry mouth/thirst, muscle cramps/weakness, slow/fast/irregular heartbeat, or confusion.

Tell your doctor right away if you have any serious side effects, including:

• very slow heartbeat
• fainting
• signs of kidney problems (such as change in the amount of urine)
• toe/joint pain
• mental/mood changes (such as depression, mood swings)
• blue fingers/toes
• new or worsening symptoms of heart failure (such as shortness of breath, swelling ankles/feet, unusual tiredness, unusual/sudden weight gain)

Get medical help right away if you have any very serious side effects, including:

• decrease in vision
• eye pain

A very serious allergic reaction to this drug is rare. However, get medical help right away 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 or at www.fda.gov/medwatch.

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 if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• liver disease
• kidney disease
• certain types of heart rhythm problems (such as a slow heartbeat, second- or third-degree atrioventricular block)
• gout
• lupus
• breathing problems (such as asthma, chronic bronchitis, emphysema)
• blood circulation problems (such as Raynaud's disease, peripheral vascular disease)
• untreated mineral imbalance (such as low potassium)
• serious allergic reactions including those needing treatment with epinephrine
• a certain muscle/nerve disease (myasthenia gravis)

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Severe sweating, diarrhea, or vomiting may cause dehydration and cause you to feel lightheaded. Tell your doctor if you have severe diarrhea or vomiting. To prevent dehydration, drink plenty of fluids unless your doctor tells you not to.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

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.

This product may prevent the fast/pounding heartbeat you would usually feel when your blood sugar level falls too low (hypoglycemia). The risk is higher if you have diabetes, or are vomiting, fasting, or not eating regularly. Other symptoms of low blood sugar level, such as dizziness and sweating, are not affected by this drug.

If you have diabetes, this product may make it harder to control your blood sugar levels. Check your blood sugar levels regularly as directed by your doctor. Tell your doctor right away if you have symptoms of high blood sugar such as increased thirst/urination. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness.

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

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using this medication. Atenolol may harm an unborn baby. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

Atenolol and chlorthalidone pass into breast milk. Atenolol may harm a nursing infant. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• dofetilide
• fingolimod
• lithium

Some products have ingredients that could raise your heart rate or blood pressure. Tell your pharmacist what products you are using, and ask how to use them safely (especially cough-and-cold products, diet aids, or NSAIDs such as ibuprofen/naproxen).

This medication may interfere with certain lab tests (such as parathyroid, protein-bound iodide), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: severe dizziness, fainting, very slow heartbeat, trouble breathing.

Do not share this medication with others.

Lifestyle changes that may help this medication work better include stress reduction programs, exercise, and dietary changes. Talk to your doctor or pharmacist about lifestyle changes that might benefit you.

Lab and/or medical tests (including kidney function, blood mineral levels such as potassium) should be done while you are taking this medication. Keep all medical and lab appointments. 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. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications 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.