Metolazone

Background

Before requesting primary care prescribing, patients must be established on a stable dose of metolazone for at least 2 weeks, with stable urea and electrolytes (including creatinine) and a stable body weight before discharge. 

Ongoing monitoring of urea and electrolytes (including creatinine) should be carried out on a monthly basis and the patients’ weight and blood pressure should be monitored at each clinic visit. 

Metolazone has an established role in the treatment of resistant oedema in heart failure where it is combined with a loop diuretic. The combination of metolazone and a loop diuretic is much more potent and needs to be initiated by someone experienced in its use and needs careful monitoring of renal function and electrolytes. It is routinely used in patients with renal impairment who do not respond to a loop diuretic. 

**Metolazone must be prescribed by brand** 

UK-licensed metolazone tablets (Xaqua) have up to two-fold difference in bioavailability compared to other (unlicensed, imported) metolazone preparations. Between 2012 and 2022, patients needing metolazone in the UK used unlicensed, imported tablets. Patients switching to the UK-licensed version may require dose adjustment depending on clinical effect; patients should be monitored for dehydration and electrolyte disturbance. 

Metolazone (Zaroxolyn 2.5mg and 5mg tablets) are an unlicensed special order, imported, product from Canada. The drug has a full monograph in the BNF with the Zaroxolyn brand listed in the medicinal forms section. 

SPC for Xaqua https://www.medicines.org.uk/emc/product/13419 

Canadian product information for Zaroxolyn https://products.sanofi.ca/en/zaroxolyn.pdf   

BNF monograph for Metolazone https://bnf.nice.org.uk/drug/metolazone.html#indicationsAndDoses   

BNF Metolazone medicinal forms section https://bnf.nice.org.uk/medicinal-forms/metolazone.html