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Metolazone 💊
Always check the BNF here for up-to-date prescribing advice.
- Thiazide-like diuretic with potent natriuretic effect.
- Typically used in combination with loop diuretics in resistant oedema.
- Short-term use is common due to risk of profound electrolyte disturbance.
⚙️ Mode of Action
- Blocks sodium reabsorption at the distal convoluted tubule (DCT), enhancing excretion of sodium, chloride, and water.
- Causes increased delivery of sodium to the distal nephron, promoting potassium and hydrogen ion excretion.
- Very potent in combination with loop diuretics due to synergistic action.
📋 Indications / Dose
- Congestive Cardiac Failure (CCF): Metolazone 2.5 mg OD (short-term, specialist supervision).
- Used for refractory oedema where loop diuretics alone are insufficient.
🔄 Interactions
- Caution with other diuretics ➝ ↑ risk of hypokalaemia, hyponatraemia, dehydration.
- Monitor electrolytes, renal function, and BP/HR closely.
- May potentiate lithium toxicity (reduced clearance).
⚠️ Cautions
- Diabetes mellitus (may worsen glycaemic control).
- Gout (may precipitate flares due to hyperuricaemia).
- Nephrotic syndrome.
- Systemic lupus erythematosus (SLE).
- Close monitoring of electrolytes, renal function, and fluid balance essential.
⛔ Contraindications
- See BNF for full list.
- Severe renal or hepatic impairment.
- Hypokalaemia, hyponatraemia, or hypovolaemia.
- Hypersensitivity to thiazides/thiazide-like diuretics.
⚡ Side Effects
- Electrolyte disturbances: ⬇️ sodium, potassium, magnesium; ⬆️ calcium, glucose, urate.
- Volume depletion ➝ hypotension, AKI, over-diuresis.
- Gout flares (due to raised uric acid).
- Metabolic alkalosis (low Cl⁻/HCO₃⁻ changes).
- Haematological: ↓ WCC, granulocytes, platelets (rare).
- Skin: Rashes, photosensitivity.
- Hepatic: Rare cholestasis.
- Pulmonary: Rare pneumonitis.
📚 References
- BNF – Metolazone
- UpToDate – “Use of metolazone in diuretic-resistant oedema.”
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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