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Flashcards in Diuretics Deck (14):

Proximal convoluted tubule (PCT)

Out --> 40-60% of NaCl, K, Water, HCO3, glucose, amino acids
In --> creatinine, antibiotics, diuretics, Uric acid
Osmotic diuretics & carbonic anhydrase inhibitors work here


Loop of henle

Out--> 25% Na, K, water, Mg, Ca
In--> nothing
Loop diuretics work here


Distal convoluted tubule (DCT)

Out--> 15% of Na, Ca, water,
In--> K, H+, urea
In the proximal part --> thiazides and PTH
In the distal part --> osmotic, K-sparing & aldosterone


Collecting duct and tubule

Out--> water
In--> nothing
Osmotic diuretics work here


Loop diuretics (furosemide,bumetanide)

Inhibit the Na/K/2Cl co-transporter in the thick ascending LOH
Prevent Na and K reabsorption causing loss of 15-25% of filtrate--> good for treating fluid salt overload
Can cause low Na,K,Ca,Mg but high urea


When to use Loop diuretics

Fluid or salt overload
Pulmonary oedema, chronic heart failure, renal failure, cirrhosis with ascites, nephrotic syndrome, hypertension if there is renal impairment, acute hypercalcaemia


Side effects of loop diuretics

Can cause low Na,K,Ca,Mg and high urea (gout)
Hypotension & metabolic alkalosis
Ototoxicity with large parenteral doses


Thiazides diuretics (bendroflumethaizide, indapamide, metolazone)

Inhibit Na/Cl cotransporter in the DCT to prevent the reabsorption of Na and Cl but also have a direct vasodilation effect.
Also decreases calcium loss
Used to treat hypertension, chronic heart failure, and can be used to prevent stone formation in idiopathic familial hypercalciuria


Side effects of thiazides

Low Na,K,Mg but high Ca, urea, glucose and lipids
Can be used paradoxically to treat nephrogenic diabetes insipidus
Use with cardiac glycosides is risky because hypercalcaemia will potentiate their action


Potassium sparing diuretics (amiloride, eperenone, triamterene)

Works by blocking apical sodium channels in the late distal tubule to prevent Na reabsorption which reduces K loss from the blood
Alone they have a weak diuretic effect but are added to others to prevent K loss


Uses of K sparing diuretics

Hypertension, heart failure, conn's syndrome, ascites, LV dysfunction secondary to MI
Add to other diuretics to block potassium loss


Side effects of K sparing diuretics

Low sodium and high potassium



Aldosterone receptor antagonist
Blocks synthesis of sodium channels and Na/K ATPase
Reduces sodium reabsorption --> slower effect than others
Useful in heart failure but can cause painful gynaecomastia


Diuretics in renal failure

If eGFR is <30ml/min a large dose of loop diuretics is required to regain get same effect as in healthy patients due to nephron hypertropy in the distal tubule
Avoid K-sparing diuretics due to risk of hyperkalaemia and thiazides are of limited use