Diuretics (Thiazide)

Question 1

Name examples of thiazide diuretics.

Answer 1

bendroflumethiazide, chlortalidone, co-triamterzide, cyclopenthiazide, indapamide, metolazone, xipamide.

Question 2

What are the indications of thiazide diuretics?

Answer 2

oedema, hypertension, heart failure.

Question 3

What are the additional indications of chlortalidone?

Answer 3

ascites due to cirrhosis in stable patients, oedema due to nephrotic syndrome, nephrogenic/partial pituitary diabetes insipidus.

Question 4

What are the contraindications of thiazide diuretics?

Answer 4

Addison’s disease, hypercalcaemia, hyponatraemia, refractory hypokalaemia, symptomatic hyperuricaemia.

Question 5

What is the mechanism of action of thiazide diuretics?

Answer 5

Thiazide diuretics inhibit sodium reabsorption at the beginning of the distal convoluted tubule, and passive accompanying absorption of chloride. This means that elimination of sodium, chloride and water increases.
They reduce blood pressure initially due to volume loss, and with long-term use the reduction in blood pressure is maintained by the vasodilatory effect of thiazides.

Question 6

What are the common/very common unwanted side effects of thiazide diuretics?

Answer 6

altered plasma-lipid concentrations, gout, hypercalcaemia, hyperglycaemia, hyperuricaemia, hypochloraemic alkalosis, hypokalaemia, hypomagnesaemia, hyponatraemia, metabolic and electrolyte disturbances, mild gastrointestinal disturbances, postural hypotension.

Question 7

What are the monitoring requirements of thiazide diuretics?

Answer 7

electrolytes should be monitored, particularly with high doses and long-term use, and in renal impairment.

Question 8

What is the patient/carer advice for co-triamterzide?

Answer 8

Advise patients that urine may look slightly blue.