metolazone: clinical use

Prescribing considerations

• Treatment is usually specialist initiated and monitored.
• Assess fluid status, renal and hepatic function, electrolyte vulnerability and interacting treatment.
• Use caution in older adults and in severe renal or hepatic impairment.
• Do not exchange preparations without clinical assessment because absorption and bioavailability are formulation dependent.

Contraindications and cautions

• Hypersensitivity to metolazone, sulfonamides, thiazides or an excipient
• Anuria
• Hepatic coma or precomatose states
• Severe electrolyte disturbance

Monitoring

• Fluid status, weight, oedema and breathlessness
• Blood pressure and postural symptoms
• Urea, creatinine and electrolytes, particularly sodium, potassium and magnesium
• Blood glucose in diabetes or latent diabetes
• Clinical response and laboratory results after changing product

Clinical pharmacology

Metolazone is a sulfonamide, thiazide-like diuretic that inhibits tubular sodium reabsorption. It undergoes little metabolism and is mainly excreted unchanged in urine; elimination is delayed when renal function is impaired.

Formulation and product differences

• The selected tablet is scored and can be divided into equal halves, but not quarters.
• The effect of food on bioavailability has not been established, so consistent administration in relation to food is advised.
• Bioavailability is formulation dependent.

Tablet

Route: Oral

Strengths: 5 mg