Merozolyn

Indications

Metolazone is a thiazide-like diuretic (water tablet) used to:

• Reduce fluid build-up (oedema) caused by heart failure, kidney disease (including when kidney function is reduced) or liver disease
• Treat high blood pressure, alone or with other medicines
• Boost the effect of a loop diuretic such as Furosemide in people with fluid overload that does not respond well to one diuretic alone, under close medical supervision

How It Works

Metolazone acts mainly on the kidney tubules to stop sodium and chloride being reabsorbed, so more salt and water are passed in the urine. This lowers the amount of fluid in the body and helps lower blood pressure. Unlike many thiazides, it still works when kidney function is poor.

Dosage and Administration

Take exactly as prescribed, usually once a day in the morning. For high blood pressure, a typical adult dose is 2.5 to 5 mg once daily. For oedema, typical doses are 5 to 10 mg once daily, sometimes up to 20 mg. When added to a loop diuretic, much smaller or less frequent doses are often used, and blood tests are needed. Different tablet types (such as 0.5 mg rapid-release and standard tablets) are not interchangeable; do not switch without your doctor's advice.

Interactions

Combined with Furosemide or other loop diuretics it can cause a very large fluid loss and dangerously low potassium or sodium. Low potassium increases the risk of heart rhythm problems with Digoxin and some antiarrhythmics. It may raise Lithium levels. NSAIDs can reduce its effect and harm the kidneys. It can raise blood sugar, so diabetes medicines may need adjusting. Steroids increase potassium loss. Other blood pressure medicines and alcohol add to dizziness.

Contraindications

Do not take metolazone if you are passing no urine (anuria), are in hepatic coma or pre-coma, have very low potassium or sodium that has not been corrected, or are allergic to metolazone or sulfonamide (sulfa) medicines.

Side Effects

Common side effects include:

• Passing urine more often
• Dizziness or light-headedness, especially when standing up
• Low potassium, sodium or magnesium, causing muscle cramps, weakness or tiredness
• Headache, nausea, loss of appetite and dry mouth
• Raised blood sugar and uric acid (which can trigger gout)
• Sensitivity to sunlight and skin rash

Get urgent medical help if you have severe dizziness or fainting, confusion, very little urine, extreme thirst, a fast or irregular heartbeat, severe muscle weakness or cramps, sudden painful swollen joint, severe skin rash or blistering, or signs of a serious allergic reaction.

Pregnancy and Lactation

Diuretics are not used for routine swelling in pregnancy and may reduce blood flow to the placenta. Use in pregnancy only if a doctor considers it necessary. Metolazone passes into breast milk and may reduce milk supply; breastfeeding is generally not recommended during treatment.

Precautions and Warnings

Your doctor will check blood salts (potassium, sodium, magnesium) and kidney function regularly, especially when it is combined with another diuretic. Weigh yourself daily if advised and report rapid weight loss. Tell your doctor if you have diabetes, gout, lupus, liver disease or kidney problems. Avoid getting dehydrated in hot weather or with vomiting or diarrhoea. Use sun protection.

Overdose

Overdose can cause severe dehydration, very low blood pressure, drowsiness, confusion, low potassium and sodium, and heart rhythm problems. Seek emergency medical care straight away.

Therapeutic Class

Thiazide-like diuretic; antihypertensive.

Storage

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