Chlorthalidone

💊 What is Chlorthalidone used for?

• •The label says chlorthalidone is used to treat high blood pressure (hypertension), either alone or together with other blood pressure medicines for more severe cases. It is also used as add-on treatment for swelling (edema) linked to congestive heart failure, liver cirrhosis, and corticosteroid or estrogen therapy. The label also says it has been found useful for swelling from some kidney conditions, including nephrotic syndrome, acute glomerulonephritis, and chronic renal failure.

How it works

The label does not explain the exact way chlorthalidone works. It describes the medicine as a diuretic, which is a medicine that increases urine output, and as an antihypertensive, which means it is used to lower blood pressure.

How it is usually taken

• •The label says a single dose is given in the morning with food, and that divided daily doses are unnecessary. The label says treatment starts with the lowest possible dose and is adjusted based on how each person responds. Follow the instructions from your prescriber or pharmacist.

Comes as

• •Tablets containing 25 mg or 50 mg of chlorthalidone. The package listed in the label is a 25 mg tablet that is white to off-white, round, unscored, and marked 'L1' on one side.

⚠️ Chlorthalidone side effects

🛑 Who should not take Chlorthalidone, and who should be careful

The label says not to take it if

• 🚨You have anuria (the kidneys make little or no urine). The label lists this as a contraindication.
• 🚨You have a known allergy (hypersensitivity) to chlorthalidone or to other sulfonamide-derived drugs.

Tell your doctor before taking it if

• •The label says to tell your doctor if you have had an allergic reaction to chlorthalidone or other diuretics, or if you have asthma.
• •Tell your doctor if you have kidney disease, liver disease, gout, or systemic lupus erythematosus.
• •Tell your doctor if you take cortisone, digitalis, lithium carbonate, or drugs for diabetes.
• •The label says to use chlorthalidone with caution in severe kidney disease, because it may cause azotemia, and cumulative effects may develop in people with impaired kidney function.
• •The label says to use caution in people with liver disease, because small changes in fluid and electrolyte balance may trigger hepatic coma.
• •The label says people with a history of allergy or bronchial asthma may have sensitivity reactions.
• •The label says diabetes medicine needs may change. Insulin needs may go up, go down, or stay the same, and higher doses of oral diabetes medicines may be needed.
• •The label says that in hot weather, edematous patients may develop low sodium (dilutional hyponatremia), and that water restriction is the appropriate therapy rather than salt, except in rare life-threatening cases.
• •The label says periodic blood tests of electrolytes should be done at appropriate intervals.

🔀 Chlorthalidone with other medicines, food and alcohol

The label says to discuss these with your doctor or pharmacist

• •Chlorthalidone may add to or increase the effect of other blood pressure medicines. The label names ganglionic peripheral adrenergic blocking drugs as having a potentiating effect.
• •Digitalis may be affected by electrolyte changes caused by chlorthalidone, and the label says digitalis therapy may make the effects of low potassium on the heart worse.
• •Corticosteroids or ACTH may increase the chance of low potassium (hypokalemia).
• •Oral diabetes medicines and insulin may need adjustment, and latent diabetes may appear during treatment.
• •Chlorthalidone may increase the body's response to tubocurarine.
• •Chlorthalidone may decrease the body's response to norepinephrine, though the label says this is not enough to stop the pressor agent from working for therapeutic use.
• •Lithium carbonate is listed in the label as a drug to tell your doctor about, but the label does not describe the specific interaction.

Alcohol and food

The label says a single morning dose with food is recommended. The label also says alcohol can increase the chance of dizziness, and that alcohol may make dizziness when standing up (orthostatic hypotension) worse.

🤰 Chlorthalidone in pregnancy and breastfeeding

Pregnancy

The label says the routine use of diuretics in healthy pregnant women is inappropriate, and that diuretics do not prevent toxemia of pregnancy. Chlorthalidone is indicated in pregnancy only when edema has pathologic causes. Animal studies found no evidence of fetal harm, but there are no adequate, well-controlled studies in pregnant women, so the label says it should be used during pregnancy only if clearly needed. The label says thiazides cross the placenta and may cause fetal or neonatal jaundice and thrombocytopenia.

Breastfeeding

The label says thiazides pass into human milk and can cause serious adverse reactions in nursing infants. A decision should be made about whether to stop nursing or stop the drug, taking into account how important the drug is to the mother.

🗓️ Storage, missed doses and taking too much

Storage

Store at 20° to 25°C (68° to 77°F). Protect from light. Keep in a tight, light-resistant container. Keep out of the reach of children.

If a dose is missed

The label does not say.

If too much is taken

The label says symptoms of acute overdose include nausea, weakness, dizziness, and disturbances of electrolyte balance. There is no specific antidote. The label recommends gastric lavage, followed by supportive treatment, which may include intravenous dextrose-saline with potassium, given with caution.

🗒️ Questions to ask about Chlorthalidone

• What dose of chlorthalidone is right for my condition, and how will it be adjusted over time?
• How often will I need blood tests to check my potassium and other electrolytes?
• Should I take this medicine with breakfast every morning, and what should I do if I have dizziness?
• Are any of my other medicines, such as diabetes medicines, lithium, digoxin, or cortisone, affected by chlorthalidone?
• How much alcohol is safe for me while taking this medicine?
• What signs of potassium loss should make me call you right away?
• If I plan a pregnancy or am breastfeeding, what should I do about this medicine?

❓ Chlorthalidone: frequently asked questions