Prescribing Notes
- Modified release indapamide 1.5mg is second line if patients develop side-effects, in particular hypokalaemia, on the IR preparation.
- Allow 4 weeks for maximal antihypertensive effect of thiazide-like diuretics.
- Both thiazide and loop diuretics can cause sodium and potassium depletion, glucose intolerance and gout. These effects are dose-related and may be more dramatic with thiazides because of their relatively long duration of action. Regular monitoring of potassium, sodium, glucose and uric acid is recommended, particularly with high doses, long term use, or in renal impairment. If potassium is persistently low, consider also measuring magnesium.
- Diuretics should not be used on a long term basis to treat simple gravitational oedema. This will usually respond to increased ambulation, raising the legs and support stockings.
- Counsel patients on ‘sick day guidance’ with diuretics
- Bendroflumethiazide is no longer a routine choice of diuretic for hypertension, but there is no need to change patients already taking it whose blood pressure is stable and well controlled. A dose of 5mg bendroflumethiazide is not recommended for hypertension.
- Metolazone should ideally only be initiated by a specialist.
- When prescribed with a loop diuretic, profound diuresis can occur and the patients should therefore be monitored carefully.
- Metolazone should be prescribed by brand. Metolazone (Xaqua®) is not interchangeable with generic unlicensed metolazone. Exercise caution when switching patients between different metolazone preparations – for further information see MHRA.
- Xaqua® tablets cannot be divided into quarters. When necessary to split tablets, this should only be into halves using the tablets score-line.
Cautions
- Thiazide and related diuretics can exacerbate diabetes, gout, and systemic lupus erythematosus.
- Thiazide diuretics lose efficacy in diuresis and BP lowering as GFR worsens, but several including indapamide, metolazone and chlorthalidone appear to remain effective at GFRs<30 ml/min per 1.73m2. See KDIGO.
- Thiazide and related diuretics should be used with caution in nephrotic syndrome, hyperaldosteronism and malnourishment
- Elderly patients are particularly susceptible to the side-effects of diuretics including increased risk of postural hypotension, collapse and falls. Confusion, dehydration, urinary incontinence and hyponatraemia may be particular problems.