Atenolol is a beta-blocker. Chlorthalidone is a thiazide diuretic (water pill).

Atenolol and chlorthalidone is a combination medicine used to treat hypertension (high blood pressure). Lowering blood pressure may lower your risk of a stroke or heart attack.

Atenolol and chlorthalidone may also be used for purposes not listed in this medication guide.

You should not use atenolol and chlorthalidone if you have a serious heart problem such as heart block or slow heart rate, if you are unable to urinate, or if you are allergic to sulfa drugs.

Do not use atenolol and chlorthalidone if you are pregnant. It could harm the unborn baby.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Your blood pressure will need to be checked often and you may need other medical tests.

Drink plenty of water each day while you are taking atenolol and chlorthalidone.

Keep using this medicine as directed, even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medicine for the rest of your life.

Your condition may need to be treated with a combination of drugs. Use all medications as directed by your doctor. Read the medication guide or patient instructions provided with each medication. Do not change your doses or medication schedule without your doctor's advice.

If you need surgery, tell the surgeon ahead of time that you are using atenolol and chlorthalidone. You may need to stop using the medicine for a short time.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using atenolol and chlorthalidone.

You should not stop using atenolol and chlorthalidone suddenly. Stopping suddenly may make your condition worse.

Some things can cause your blood pressure to get too low. This includes vomiting, diarrhea, or heavy sweating. Call your doctor if you are sick with vomiting or diarrhea.

If you do stop taking this medicine, limit your physical activity to prevent heart problems.

Store at room temperature away from moisture, heat, and light.

Usual Adult Dose for Hypertension:

Initial dose: Atenolol 50 mg-Chlorthalidone 25 mg orally once a day
Maintenance dose: Atenolol 50 to 100 mg-Chlorthalidone 25 mg orally once a day

Use: Treatment of hypertension if the fixed dose combination represents an appropriate dose for the individual patient.

You should not use this medicine if you are allergic to atenolol or chlorthalidone, or if you have:

• a serious heart condition such as "AV block" (second or third degree);

• very slow heartbeats;

• heart failure;

• if you are unable to urinate; or

• if you are allergic to sulfa drugs.

Tell your doctor if you have ever had:

• congestive heart failure;

• coronary artery disease (hardened arteries);

• angina (chest pain);

• asthma, bronchitis, or other lung disorder;

• diabetes;

• a thyroid or parathyroid disorder;

• liver or kidney disease;

• pheochromocytoma (tumor of the adrenal gland);

• gout;

• lupus;

• peripheral vascular disease such as Raynaud's syndrome;

• psoriasis;

• an electrolyte imbalance (such as low levels of potassium in your blood); or

• allergies (or if you are undergoing allergy treatments or skin-testing).

Tell your doctor if you are pregnant or you become pregnant. Taking atenolol and chlorthalidone during the second or third trimester of pregnancy may cause low birth weight, slow heartbeats, or or low blood sugar in the newborn.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk. If you do breastfeed, tell your doctor if you notice symptoms such as weakness, unusual hunger, fussiness, or sweating in the nursing baby.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include nausea, extreme weakness, wheezing, chest tightness, trouble breathing, slow heartbeats, swelling, rapid weight gain, feeling light-headed, or fainting.

Avoid becoming overheated or dehydrated during exercise, in hot weather, or by not drinking enough fluids. Follow your doctor's instructions about the type and amount of liquids you should drink. In some cases, drinking too much liquid can be as unsafe as not drinking enough.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Atenolol and chlorthalidone may cause serious side effects. Call your doctor at once if you have:

• new or worsening chest pain;

• slow or uneven heartbeats;

• a light-headed feeling, like you might pass out;

• shortness of breath (even with mild exertion), swelling, rapid weight gain;

• cold feeling in your hands and feet;

• jaundice (yellowing of the skin or eyes);

• low sodium level --headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady; or

• low potassium level--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling.

Common side effects of atenolol and chlorthalidone may include:

• slow heartbeats;

• feeling weak or tired;

• dizziness, drowsiness;

• numbness or tingling;

• pale skin, bruising or bleeding;

• depression; or

• upset stomach, loss of appetite, constipation.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all your current medicines. Many drugs can affect atenolol and chlorthalidone, especially:

• digoxin, digitalis;

• indomethacin;

• insulin;

• lithium;

• any other beta-blocker--bisoprolol, carvedilol, labetalol, metoprolol, nebivolol, propranolol, sotalol, timolol, and others; or

• heart or blood pressure medication--amiodarone, clonidine, diltiazem, disopyramide, nicardipine, nifedipine, reserpine, verapamil, and others.

This list is not complete and many other drugs may affect atenolol and chlorthalidone. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.