Medicines Healthcare Products Regulatory Agency
Advice for healthcare professionals:
- healthcare professionals have expressed concerns about switching patients between metolazone preparations due to potential differences in the bioavailability and dosing instructions between products
- follow good practice in prescribing medicines by considering the licensed formulation (Xaqua) in preference to unlicensed imported metolazone preparations in new patients
- assess individual patient factors before switching patients from unlicensed imported metolazone products to Xaqua
- consider dose adjustment, due to potential differences in bioavailability, at the time of switching from unlicensed imported metolazone products to Xaqua
- monitor patients to assess the clinical impact of the switch monitoring should be done on an individual basis after an assessment of the patients risk, and could include assessment of blood pressure, electrolytes and degrees of oedema and breathlessness
- do not divide Xaqua tablets into quarters when it is necessary to split tablets, this should be only into halves using the tablet score-line
- tell the patient if their prescribed dose means that they have to split their Xaqua tablet and ensure that this is documented clearly on the medication label and in medication records where appropriate
- prescribe and supply metolazone by product name and document this clearly, especially for transfers of care
- report suspected adverse drug reactions associated with metolazone on a Yellow Card
Advice for healthcare professionals to give to patients and carers:
- if you currently use an imported unlicensed metolazone product your doctor will assess your suitability to be switched to Xaqua
- do not use different metolazone preparations at the same time
- be aware of the brand of metolazone you are prescribed and ask your healthcare professional about any changes they make to your prescription
- be aware if your dose of metolazone means the tablets need to be split and if these will be dispensed to you already split or if you need to split the tablets yourself
- be aware of the dosing instructions for your metolazone tablets switching to Xaqua may require you to change from taking your tablets once a day to alternate days
- you may need additional blood tests and checks of your blood pressure and weight when you are switched to Xaqua
- be aware of the warning signs and symptoms of electrolyte imbalance which could occur on switching metolazone products and contact a healthcare professional if you experience these (symptoms include: dry mouth; thirst; weakness; lethargy; drowsiness; restlessness; muscle pains or cramps; muscle fatigue; low blood pressure; low urine volume; racing heartbeat and gastrointestinal disturbances such as nausea and vomiting)
- be aware of the signs and symptoms you might experience if the dose of your medication is too low and contact a healthcare professional if you experience these (symptoms include increasing breathlessness, weight gain and worsening swelling of the extremities)
- do not stop your treatment without discussing with your doctor first
- if you experience any side effects, please report them to the Yellow Card scheme
About metolazone
Metolazone is a sulphonamide with thiazide-like diuretic properties indicated for the treatment of hypertension and oedema. Treatment is usually initiated and monitored by specialists.
In recent years, metolazone was supplied to the UK as an unlicensed import from other countries in which it held a licence. As such, it was only prescribed to patients when clinically necessary. In February 2021, Renascience Pharma Ltd received UK marketing approval for a new metolazone product: Xaqua 5 milligram (mg) Tablets.
The Xaqua Summary of Product Characteristics advises a dose of 2.5mg to 5mg per day for the licensed indications of hypertension and oedema related to congestive heart failure or kidney disease. These doses may be adjusted according to the individual response of the patient.
Healthcare professionals have expressed concerns to the MHRA with respect to switching patients between metolazone preparations due to potential differences in the bioavailability and dosing instructions between Xaqua and unlicensed imported metolazone preparations.
The Specialist Pharmacy Services (SPS) recently published guidance to healthcare professionals on the differences between metolazone preparations and safety considerations.[footnote 1]
The MHRA sought independent advice from Expert Advisory Groups of the Commission on Human Medicines, which recommended that the Marketing Authorisation Holder for Xaqua circulate a letter to healthcare professionals to reinforce key messages about initiating metolazone treatment or switching to Xaqua. In addition, the product information for Xaqua has been updated to clarify that references to comparative bioavailability with other metolazone products relate specifically to Metenix (a formerly licenced product, which was withdrawn in the UK in March 2012 for commercial reasons) and not to any other metolazone preparations. Metenix is the only product for which there is comparative bioavailability data.
Advice on initiating metolazone
Specialists are advised to prescribe the licensed product Xaqua when initiating metolazone treatment rather than an unlicensed imported metolazone preparation.
Currently, there is no national UK guidance on the use of metolazone. However, local guidance may be available in the form of shared care, prescribing and monitoring and/or clinical specialty guidelines.
Individual patient factors should be considered before initiating metolazone treatment. These include:
- the indication, co-morbidities and concomitant treatments
- the patients degree of fragility and ability to tolerate potential fluid and electrolyte imbalances
- the risk of side effects from excessive or sub-therapeutic dosing
- what monitoring arrangements are in place
- the patients ability to manage the handling of partial tablets (halving) or alternate day dosing regimens
- the patients understanding of the treatment and when to contact a healthcare professional
Arrangements for clinical monitoring should be made on an individual basis after an assessment of the individual clinical risk. Relevant parameters for monitoring include blood urea, electrolytes and creatinine, blood pressure and weight. The frequency of monitoring should be based on the individual patient.
Advice on switching to Xaqua
Specialists should manage the switching of patients already taking an unlicensed imported metolazone product to Xaqua. The individual patient factors listed in the previous section should be considered. Arrangements for monitoring should be made on an individual basis after an assessment of the individual clinical risk.
If switching to Xaqua is appropriate, the dose of metolazone provided as Xaqua may need to be adjusted to take account of individual patient factors, and the difference in bioavailability between Xaqua and the metolazone preparation being replaced (where that information is available).
In the absence of comparative bioavailability data to inform a dose recommendation, an option may be to reduce the dose by half (from unlicensed metolazone to Xaqua) and/or adjust the frequency of dosing of Xaqua (for example, from unlicensed metolazone daily to Xaqua on alternate days). The dose can then be titrated upwards under increased monitoring, if necessary.
Advice on continuing treatment with unlicensed metolazone
If switching is not considered clinically appropriate it should be highlighted to the patient precisely which metolazone preparation they are receiving (including manufacturer, brand name (if available) and dose). The prescription and supply of metolazone should be product-specific and documented clearly, especially for transfers of care.
Report suspected drug reactions on a Yellow Card
Please continue to report suspected adverse drug reactions to the Yellow Card scheme.Healthcare professionals, patients, and caregivers are asked to submit reports using the Yellow Card scheme electronically using:
- the Yellow Card website
- the Yellow Card app; download from the Apple App Store or