Diuretics Flashcards
Thiazides are used to
relieve oedema due to chronic heart failure +, in lower doses, to reduce blood pressure.
L diuretics are used in
pulmonary oedema due to left ventricular failure + in patients with chronic heart failure.
Combination diuretic therapy may be effective in patients with
oedema resistant to treatment with 1 diuretic. Vigorous diuresis, particularly with loop diuretics, may induce acute hypotension; rapid reduction of plasma volume should be avoided
Thiazides and related compounds are
moderately potent diuretics;
~ inhibit sodium reabsorption at beginning of distal convoluted tubule. ~ act within 1-2 hours of oral administration
~ duration of action of 12-24 hours;
~ usually administered early in day so that diuresis does not interfere with sleep.
Thiazides and HTN
low dose of thiazide = maximal or near-maximal BP lowering effect, with very little biochemical disturbance. Higher doses cause more marked changes in plasma potassium, sodium, uric acid, glucose, and lipids, with little advantage in BP control.
~ Chlortalidone & indapamide = preferred diuretics
Bendroflumethiazide can be used for
mild or moderate heart failure;
~ licensed for tx of HTN but no longer considered first-line diuretic for this indication, although patients with stable and controlled BP currently taking bendroflumethiazide can continue treatment.
Chlortalidone is
~ thiazide-related compound
~ longer duration of action than thiazides
~ may be given on alternate days to control oedema
~ also useful if acute retention liable to be precipitated by more rapid diuresis or if patients dislike altered pattern of micturition caused by other diuretics
~ can also be used under close supervision for treatment of ascites due to cirrhosis in stable patients.
Xipamide & indapamide are
chemically related to chlortalidone.
~ Indapamide lower BP with less metabolic disturbance, particularly less aggravation of diabetes
Metolazone
~ particularly effective when combined with loop diuretic (even in severe renal failure)
Loop diuretics are used in
~ pulmonary oedema due to left ventricular failure; IV administration produces relief of breathlessness + reduces pre-load sooner than would be expected from time of onset of diuresis.
~ also used in chronic heart failure
~ Diuretic-resistant oedema (except lymphoedema & oedema due to peripheral venous stasis or CCB) treated with loop diuretic + thiazide or related diuretic (e.g. bendroflumethiazide or metolazone).
If necessary, loop diuretic added to antihypertensive tx to achieve better control of BP in resistant HTN, or in patients with impaired renal function or heart failure.
~ can exacerbate diabetes (but hyperglycaemia less likely than thiazides) + gout.
~ If enlarged prostate, urinary retention can occur, although less likely if small doses & less potent diuretics used initially
Furosemide & bumetanide are
~ both act within 1 hour of taking
~ diuresis complete within 6 hours so that, if necessary, can be given BD in 1 day without interfering with sleep.
~ Following IV administration furosemide = peak effect ~30 minutes
~ dose-related diuresis
K-sparing diuretics + mineralocorticoid receptor antagonists (MRA)
~ Amiloride + triamterene on their own = weak diuretics
~ cause retention of K so given with thiazide / loop as more effective alternative to potassium supplements.
~ Potassium supplements NOT given with K- sparing diuretics.
~ K-sparing diuretic + ACE / ARBs = severe hyperkalaemia.
Mineralocorticoid receptor antagonists ~ spironolactone
~ potentiates thiazide or loop diuretics by antagonising aldosterone; ~ K-sparing diuretic.
~ GOOD in tx of oedema + ascites caused by liver cirrhosis ; furosemide used.
~ Low doses good in moderate-severe heart failure & when used in resistant hypertension [unlicensed].
~ also used in primary hyperaldosteronism (Conn’s syndrome)
~ given before surgery or if surgery not appropriate, in lowest effective dose for maintenance.
Eplerenone is
~licensed for left ventricular dysfunction with evidence of heart failure after MI
~ licensed as adjunct in chronic mild heart failure with left ventricular systolic dysfunction.
~ Potassium supplements must not be given with mineralocorticoid receptor antagonists.
Mannitol
osmotic diuretic
~ used to treat cerebral oedema + raised intra-ocular pressure
Acetazolamide
~ carbonic anhydrase inhibitor
~ weak diuretic + not used much as diuretic
~ prophylaxis against mountain sickness [unlicensed] but not substitute for acclimatisation
~ use in glaucoma
when are diuretics taken
morning to avoid sleep disturbance
Loop diuretics e.g.
Bumetanide (most potent)
Furosemide (gout)
Torasemide (musculoskeletal pain)
Diuretics how to take
Morning to avoid sleep disturbances
Loop diuretic e.g.
- Bumetanide (most potent)
- Furosemide (exacerbate gout )
- Torsemide (musculoskeletal pain)
Thiazide diuretics e.g.
Bendroflumethiazide
Cyclopenthiazide
Thiazide-like diuretics e.g.
- Chlortalidone (long half life)
- indapamide (less aggregating of diabetes)
- Metolazone (works in severe renal failure)
- Xipamide
K-sparing diuretics
- Amiloride
- Triamterene (blue urine in some lights)
Aldosterone antagonist diuretics e.g.
- Spironolactone (ascites in liver failure!)
- Eplerenone (used in post-acute MI)
