The thiazide diuretics (bendroflumethiazide, chlortalidone, metolazone, indapamide, xipamide) are used to relieve oedema associated with heart failure and to treat hypertension.

Dosage regimen

* Thiazides usually act within one to two hours, with a duration of action between 12 and 24 hours, so should be taken in the morning to avoid diuresis interfering with sleep. The exception is chlortalidone which has a longer duration of action so it may be taken on alternate days.

Patient's knowledge of the medicine's use

* Diuretics are usually employed first-line for patients with symptoms of acute pulmonary oedema. Dosage can be titrated up or down according to response and need following the introduction of further heart failure therapies.

* Thiazides may be used - either alone or in combination with other drugs - for hypertension. Doses are usually lower than those used in heart failure.

Is the medicine working?

* Has the patient been taking the correct dosage of their medication?

* Has the patients symptoms/condition deteriorated? If so, refer back to the prescriber.

* Is the patient taking any OTC/herbal remedies, which may interact with their medication?

Side effects

* Diuretics can precipitate hypokalaemia which can be dangerous in patients also receiving digoxin. Lower doses of diuretics should be used in the elderly and in patients with impaired renal function. Other side effects of diuretics include mild GI disturbances and postural hypotension.

* Thiazides can exacerbate diabetes and gout.

Monitoring

* Electrolytes should be monitored with patients who are on thiazides long-term, who have renal impairment or who are on high doses.

Lifestyle

* Advise patients on the need to maintain a healthy lifestyle, including reducing salt and alcohol intake, cutting down on smoking, eating a balanced diet and taking regular exercise.

* Advise patients that they may be eligible for a one-off pneumococcal vaccination and a yearly flu vaccination.

Kevin Alexander, community pharmacist, Hafod Pharmacy, Swansea / AF

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