Thalide

Indications

• High blood pressure (hypertension), alone or with other blood pressure medicines.
• Swelling caused by fluid build-up (oedema) linked to heart failure, liver disease, kidney disease or long-term steroid use.

Specialists sometimes use it for other conditions, such as preventing some kidney stones, as prescribed.

How It Works

Chlorthalidone is a thiazide-like diuretic (water tablet). It makes the kidneys remove more salt and water from the body. This reduces fluid in the blood vessels and lowers blood pressure. Its effect lasts more than a day.

Dosage and Administration

High blood pressure, adults: usually 12.5 mg to 25 mg once a day in the morning. The doctor may raise it to 50 mg if needed.

Fluid swelling, adults: usually 25 mg to 50 mg once a day or on alternate days, as prescribed. Higher doses are used only under close supervision.

Take it in the morning with food so you do not need to pass urine at night. Older people may start with a lower dose. Children: only as prescribed.

If a dose is missed, take it when you remember the same morning; if it is late in the day, skip it. Do not take two doses together.

Interactions

• Lithium: levels can rise to harmful amounts.
• Other blood pressure medicines: blood pressure may fall too much at first.
• Painkillers such as Diclofenac or Naproxen: reduce its effect and can harm the kidneys.
• Digoxin: low potassium caused by Chlorthalidone increases the risk of Digoxin side effects.
• Steroids and laxatives: more potassium loss.
• Diabetes medicines: the dose may need adjusting because blood sugar can rise.

Contraindications

• Allergy to Chlorthalidone or to sulphonamide ("sulfa") medicines
• Severe kidney failure or no urine production
• Severe liver failure
• Low potassium or sodium that does not correct, or high calcium in the blood
• Active gout

Side Effects

Common: low potassium (weakness, cramps), low sodium, dizziness on standing, raised uric acid or gout, higher blood sugar and cholesterol, upset stomach, skin more sensitive to sunlight and erection problems.

Get medical help at once for severe muscle weakness or cramps, an irregular or racing heartbeat, confusion or fits, fainting, extreme thirst with very little urine, a severe skin rash, or swelling of the face and trouble breathing.

Pregnancy and Lactation

Chlorthalidone is not used for ordinary swelling or routine blood pressure control in pregnancy; it is used only if a doctor decides it is needed. It passes into breast milk and may reduce milk supply, so it is best avoided while breastfeeding unless a doctor advises it.

Precautions and Warnings

• Blood tests for potassium, sodium and kidney function are needed from time to time.
• Take care if you have diabetes, gout, lupus or liver disease.
• Drink enough fluids; tell your doctor if you have vomiting, diarrhoea or heavy sweating.
• Get up slowly to avoid dizziness, especially older people.
• Use sun protection.

Overdose

Too much can cause dizziness, nausea, weakness, dehydration, very low blood pressure and salt imbalances. Contact a doctor or go to hospital straight away.

Therapeutic Class

Diuretic (thiazide-like) and antihypertensive.

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.