diuretics (oedema)

Question 1

what are thiazide- like diuretics used for

name some examples of thiazide-like diuretics

Answer 1

• oedema in chronic heart failure (e.g 5-10mg)
• to reduce blood pressure (in lower doses e.g 2.5mg)

examples:
bendroflumethiazide, indapamide, chlortalidone

Question 2

what are loop diuretics used for

name some examples of loop diuretics

Answer 2

• pulmonary oedema due to left ventricular failure
• in patients with chronic heart failure

examples:
furosemide, bumetanide, torasemide

Question 3

when would combination diuretic be used

Answer 3

patients with oedema resistant to treatment with one diuretic

note vigorous diuresis, particularly with loop diuretics, may induce acute hypotension so rapid reduction of plasma volume should be avoided

Question 4

what is the mechanism of action for thiazide-like diuretics

Answer 4

inhibit sodium reabsorption at the beginning of the distal convoluted tubule. They act within 1-2 hrs of oral administration

Question 5

why are thiazide-like diuretics usually administered early in the day

Answer 5

so that the diuresis (increased urine production) does not interfere with sleep. They have a duration of action of 12-24 hours

Question 6

which thiazide-like diuretics are preferred for management of hypertension

Answer 6

Chlortalidone and indapamide

Question 7

what is bendroflumethiazide (a thiazide-like diuretic) used for

Answer 7

• used for mild to moderate heart failure
• note it is no longer the first-line diuretic for hypertension but can be continued for this if patients were already taking it*

Question 8

why is chlortalidone (a thiazide-like diuretics) administered on alternate days

Answer 8

has a longer duration of action than the other thiazides and may be given on alternate days to control oedema

Question 9

what is the advantage of using indapamide to lower blood pressure over other thiazide-like diuretics

Answer 9

because it lowers blood pressure with less metabolic disturbance, particularly less aggravation of diabetes mellitus

Question 10

why are lower doses of thiazide-like diuretics used to control hypertension

Answer 10

because a low doses you get the maximum blood pressure lowering effect with very little biochemical disturbance.

at higher doses, the blood pressure lowering effect stays the same but you get biochemical disturbance (e.g plasma potassium, sodium, uric acid, glucose, and lipids)

Question 11

which thiazide-like diuretic is effective even in renal failure

Answer 11

Metolazone (which is effective when combined with loop diuretics)

Question 12

what is the benefit seen when a loop diuretic is administered by I.V

Answer 12

produces relief of breathlessness and reduces pre-load sooner than would be expected from the time of onset of diuresis (increased urine production)

Question 13

when would you combine the use of a thiazide-like diuretic + loop diuretic

Answer 13

Diuretic-resistant oedema (except lymphoedema and oedema due to peripheral venous stasis or calcium-channel blockers)

Question 14

what are the disadvantages of using loop diuretics

Answer 14

• they can exacerbate diabetes + gout
• can cause urinary retention in patients with an enlarged prostate
• can cause HYPOkalaemia + HYPOmagnesaemia

Question 15

which type of diuretic can exacerbate diabetes + gout

Answer 15

loop diuretics

examples of loop diuretics = furosemide, bumetanide

Question 16

which type of diuretic is less likely to exacerbate diabetes

Answer 16

thiazide-like diuretics (because they are less likely to cause hyperglycaemia)

Question 17

why can furosemide + bumetanide (loop diuretics) be given twice a day without interfering with sleep

Answer 17

because they both act within 1 hour of oral administration and diuresis (increased urine production) is complete within 6 hours

*note patients only given twice a day if necessary)

Question 18

why are Amiloride hydrochloride + Triamterene (potassium-sparing diuretics) given in combination with other diuretics such as loop or thiazide-like

Answer 18

because on their own, they are weak diuretics. but when used in combination with loop or thiazide-like, they are more effective than taking potassium supplements because they cause retention of potassium

Question 19

which supplements MUST NOT be given with potassium-sparing diuretics

Answer 19

potassium supplements

Question 20

why must you AVOID administering a potassium-sparing diuretic in patients taking ACE inhibitors or ARBS

Answer 20

because it can cause severe hyperkalemia

Question 21

name examples of aldosterone antagonist diuretics

Answer 21

• spironolactone (also a potassium sparing diuretic)

- eplerenone

Question 22

which supplements MUST NOT be given with aldosterone antagonist diuretics

Answer 22

potassium

Question 23

what is spironolactone (aldosterone antagonist + potassium-sparing diuretic) used for

Answer 23

• oedema and ascites caused by cirrhosis of the liver
• moderate to severe heart failure
• resistance hypertension (unlicensed)
• primary hyperaldosteronism (Conn’s syndrome)

Question 24

what is eplerenone used for

Answer 24

• adjunct in left ventricular dysfunction with evidence of heart failure after a myocardial infarction
• adjunct in chronic mild heart failure with left ventricular systolic dysfunction.

Question 25

potassium-sparing diuretics are not usually necessary in routine treatment of hypertension so when would they be used?

Answer 25

if hypokalaemia (low potassium) develops