2.2.1 Thiazides and related diuretics

Choice

DrugDosage
1st choiceIndapamide tablets
2.5mg; m/r tablets 1.5mg
Dose:
Hypertension – 2.5mg once daily (or m/r 1.5mg once daily).

Prescribing Notes

  • 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.
  • Allow 4 weeks for maximal antihypertensive effect of thiazide-like diuretics.
  • A dose of 5mg bendroflumethiazide is not recommended for hypertension. It has no benefit over 2.5mg in lowering blood pressure but increases the risk of side effects. Patients prescribed bendroflumethiazide 5mg for hypertension should be reviewed.
  • 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. If potassium is persistently low, consider also measuring magnesium.
  • Patients receiving thiazide diuretics should be monitored carefully for hypokalaemia particularly if used as monotherapy.

Other diuretics:

  • Chlortalidone is recommended by NICE for the management of hypertension. It is not currently a formulary choice due to practical issues (requirement to cut tablets and supply problems).
  • Metolazone should only be initiated in secondary care; profound diuresis can occur and the patients should therefore be monitored carefully. It is only available from ‘special-order’ manufacturers or specialist importing companies.

Cautions

  • Thiazide and related diuretics can exacerbate diabetes, gout, and systemic lupus erythematosus. Electrolytes should be monitored particularly with high doses, long term use, or in renal impairment.
  • Thiazides are ineffective if eGFR is less than 30mL/minute/1.73m2 and should be avoided; metolazone remains effective but with a risk of excessive diuresis and should only be initiated in secondary care.
  • 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.
  • There is a risk of non-melanoma skin cancer with hydrochlorothiazide, particularly in long-term use. For further details see MHRA.
  • 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 – click here for further information