diuretics

Question 1

mannitol, isosorbide, glycerol

Answer 1

Osmotic Diuretics: inert molecules which are free filtered and not reabsorbed or secreted as there is no interaction with transport system
SOA proximal tubule
MOA to retain fluid by osmotic pressure when Na/Cl leave, results in high volume isotonic urine
used in renal failure, intra-cranial pressure reduction, and glucose is present in urine in diabetes

Question 2

acetozolamide

Answer 2

Carbonic Anhydrase Inhibitors - Na/H exchange in PT, inhibit catecholamines in PT cells, inhibits the re-absorption of HCO3 thus less H available for exchange, weak diuretic, form of osmotic diuretic, used in glaucoma

Question 3

furosemide, ethacrynic acid, bumetanide

Answer 3

Loop diuretics - primarily inhibit NaCl re-absorption from the thick segment of the medullary ascending limb, inhibits the Na/2Cl/K cotransporter, arrives at the site by being freely filtered AND organic acid secretory system of PT, potent diuresis of isotonic urine, used in hypertension and pulmonary oedema, has a rapid onset between 1-4 hr duration, increased rate of NaCl delivery to distal tubule increases K secretion.excretion (Na out, K in), side effects of hyperurricaemia (saturation of acid system) and K depletion

Question 4

chlorthiazide, hydrochlorothiazide, chlorthalidone

Answer 4

Thiazide diuretics - organic anions (organic acid secretory system), used in hypertension and mild heart failure, Na-Cl cotransporter blocked by thiazides, act on early distal tubule, delivery of Na to the more distal Na/K exchange increased thus K secretion is enhanced, thiazides are less potent than loop diuretics, long lasting action

Question 5

triamterene, amiloride

Answer 5

Na channel blockers - similar effects to spironolactone, reduces Na absorption and H/K secretion in DT, blocks entry of Na into tubule cells across luminal cell membrane by blocking Na selective channels, decreases the Na-K exchange, action is independent of aldosterone (used in addissons), little diuretic action

Question 6

spironolactone

Answer 6

Aldosterone antagonists - aldosterone promotes absorption of Na and secretion of H/K, sprionolactone competes with aldosterone sides in principle cells of collecting duct, spironolactone/receptor complex is inactive and thus cannot stimulate Na/K exchange, reduces the K excretion produced by other diuretics, used when aldosterone is present in excess