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 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.

Use Tenoretic 50 (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

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

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 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.

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.