Chlorthalidone, a ‘water pill,’ is used to treat high blood pressure and fluid retention caused by various conditions, including heart disease. It causes the kidneys to get rid of unneeded water and salt from the body into the urine.

This medicine is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Chlorthalidone comes as a tablet to take by mouth. It usually is taken once a day or every other day after a meal, preferably breakfast. It is best to take this medicine in the morning to avoid going to the bathroom during the night. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take chlorthalidone exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Chlorthalidone controls high blood pressure but does not cure it. Continue to take chlorthalidone even if you feel well. Do not stop taking chlorthalidone without talking to your doctor.

Chlorthalidone may also be used to treat patients with diabetes insipidus and certain electrolyte disturbances and to prevent kidney stones in patients with high levels of calcium in their blood. Talk to your doctor about the possible risks of using this medicine for your condition.

Before taking chlorthalidone,

• Tell your doctor and pharmacist if you are allergic to chlorthalidone, sulfa drugs, or any other drugs.
• Tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially other medicines for high blood pressure, anti-inflammatory medications such as ibuprofen (Motrin, Nuprin) or naproxen (Aleve), corticosteroids (e.g., prednisone), lithium (Eskalith, Lithobid), medications for diabetes, probenecid (Benemid), and vitamins. If you also are taking cholestyramine or colestipol, take it at least 1 hour after chlorthalidone.
• Tell your doctor if you have or have ever had diabetes, gout, or kidney, liver, thyroid, or parathyroid disease.
• Tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking chlorthalidone, call your doctor immediately.
• If you are having surgery, including dental surgery, tell the doctor or dentist that you are taking chlorthalidone.
• You should know that this drug may make you drowsy. Do not drive a car or operate machinery until you know how this drug affects you.
• Remember that alcohol can add to the drowsiness caused by this drug.
• Plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen. Chlorthalidone may make your skin sensitive to sunlight.

Follow your doctor’s directions. They may include following a daily exercise program or a low-salt or low-sodium diet, potassium supplements, and increased amounts of potassium-rich foods (e.g., bananas, prunes, raisins, and orange juice) in your diet.

Take the missed dose as soon as you remember it. However, if it is almost time for your 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.

Frequent urination should go away after you take chlorthalidone for a few weeks.

Tell your doctor if any of these symptoms are severe or do not go away:

• Muscle weakness
• Dizziness
• Cramps
• Thirst
• Stomach pain
• Upset stomach
• Vomiting
• Diarrhea
• Loss of appetite
• Headache
• Hair loss

If you experience any of the following symptoms, call your doctor immediately:

• Sore throat with fever
• Unusual bleeding or bruising
• Severe skin rash with peeling skin
• Difficulty breathing or swallowing

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medicine in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Keep all appointments with your doctor and the laboratory. Your blood pressure should be checked regularly, and blood tests should be done occasionally.

Do not let anyone else take your medicine. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.