diuretics (oedema) Flashcards
what are thiazide- like diuretics used for
name some examples of thiazide-like diuretics
- oedema in chronic heart failure (e.g 5-10mg)
- to reduce blood pressure (in lower doses e.g 2.5mg)
examples:
bendroflumethiazide, indapamide, chlortalidone
what are loop diuretics used for
name some examples of loop diuretics
- pulmonary oedema due to left ventricular failure
- in patients with chronic heart failure
examples:
furosemide, bumetanide, torasemide
when would combination diuretic be used
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
what is the mechanism of action for thiazide-like diuretics
inhibit sodium reabsorption at the beginning of the distal convoluted tubule. They act within 1-2 hrs of oral administration
why are thiazide-like diuretics usually administered early in the day
so that the diuresis (increased urine production) does not interfere with sleep. They have a duration of action of 12-24 hours
which thiazide-like diuretics are preferred for management of hypertension
Chlortalidone and indapamide
what is bendroflumethiazide (a thiazide-like diuretic) used for
- 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*
why is chlortalidone (a thiazide-like diuretics) administered on alternate days
has a longer duration of action than the other thiazides and may be given on alternate days to control oedema
what is the advantage of using indapamide to lower blood pressure over other thiazide-like diuretics
because it lowers blood pressure with less metabolic disturbance, particularly less aggravation of diabetes mellitus
why are lower doses of thiazide-like diuretics used to control hypertension
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)
which thiazide-like diuretic is effective even in renal failure
Metolazone (which is effective when combined with loop diuretics)
what is the benefit seen when a loop diuretic is administered by I.V
produces relief of breathlessness and reduces pre-load sooner than would be expected from the time of onset of diuresis (increased urine production)
when would you combine the use of a thiazide-like diuretic + loop diuretic
Diuretic-resistant oedema (except lymphoedema and oedema due to peripheral venous stasis or calcium-channel blockers)
what are the disadvantages of using loop diuretics
- they can exacerbate diabetes + gout
- can cause urinary retention in patients with an enlarged prostate
- can cause HYPOkalaemia + HYPOmagnesaemia
which type of diuretic can exacerbate diabetes + gout
loop diuretics
examples of loop diuretics = furosemide, bumetanide
which type of diuretic is less likely to exacerbate diabetes
thiazide-like diuretics (because they are less likely to cause hyperglycaemia)
why can furosemide + bumetanide (loop diuretics) be given twice a day without interfering with sleep
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)
why are Amiloride hydrochloride + Triamterene (potassium-sparing diuretics) given in combination with other diuretics such as loop or thiazide-like
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
which supplements MUST NOT be given with potassium-sparing diuretics
potassium supplements
why must you AVOID administering a potassium-sparing diuretic in patients taking ACE inhibitors or ARBS
because it can cause severe hyperkalemia
name examples of aldosterone antagonist diuretics
- spironolactone (also a potassium sparing diuretic)
- eplerenone
which supplements MUST NOT be given with aldosterone antagonist diuretics
potassium
what is spironolactone (aldosterone antagonist + potassium-sparing diuretic) used for
- oedema and ascites caused by cirrhosis of the liver
- moderate to severe heart failure
- resistance hypertension (unlicensed)
- primary hyperaldosteronism (Conn’s syndrome)
what is eplerenone used for
- 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.
potassium-sparing diuretics are not usually necessary in routine treatment of hypertension so when would they be used?
if hypokalaemia (low potassium) develops