Pharmacology 1: Oedema and Diuretics

Question 1

in general terms, what causes oedema

Answer 1

imbalance between rate of formation and absorption of interstitial fluid

Question 2

what are the 2 main forces that drive water out of capillaries

Answer 2

hydrostatic pressure of capillaries (and oncotic pressure of plasma)

Question 3

what main forces drive water back into capillaries

Answer 3

oncotic (osmotic) pressure of capillaries - mainly driven by plasma proteins (and hydrostatic pressure of interstitial fluid)

Question 4

what happens when you increase hydrostatic pressure of the capillaries

Answer 4

the fluid travels down it’s concentration gradient to the interstitial fluid - creating oedema

Question 5

what happens when you decreases interstitial oncotic pressure

Answer 5

the interstitial fluid is more dilute so there is less driving force for the fluid back into the capillaries

Question 6

how does nephrotic syndrome cause oedema, decreased blood volume and decreased CO

Answer 6

1) disorder of glomerular filtration allows large proteins to be lost in urine 2) these proteins are lost from the blood which decreases oncotic pressure of capillaries 3) this creates oedema

Question 7

how does congestive heart failure cause pulmonary and peripheral oedema

Answer 7

1) reduced CO and subsequent renal hypofusion 2) RAAS activates 3) increased hydrostatic pressure of capillaries causes oedema

Question 8

how does hepatic cirrhosis with ascites cause oedema

Answer 8

1) resistance of blood in hepatic portal vein to liver 2) decreased circulating albumin 3) decreased oncotic pressure of capillaries 4) RAAS activated

Question 9

what are the 2 main uses of diuretics

Answer 9

increase urine flow and to enhance excretion of water and salt in oedema

Question 10

how is sodium reabsorbed in the proximal convoluted tubule

Answer 10

passive Na+Cl- reabsorption and Na/H exchanger catalysed by carbonic anhydrase

Question 11

which diuretic is used to block Na reabsorption in the proximal convoluted tubule

Answer 11

carbonic anhydrase inhibitors

Question 12

how is sodium reabsorbed in the thick ascending loop of Henle and which diuretic blocks it

Answer 12

Na/K/2Cl co transporter - loop diuretics

Question 13

how is sodium reabsorbed in the early distal convoluted tubule

Answer 13

Na/H exchange (carbonic anhydrase) and NaCl cotransporter (thiazide diuretics)

Question 14

how is sodium reabsorbed in the collecting ducts

Answer 14

Na/K exchange (potassium sparing diuretics)

Question 15

on which membrane do most diuretics act on

Answer 15

apical membrane of tubular cells

Question 16

by which 2 mechanisms to diuretics enter the filtrate

Answer 16

glomerular filtration and secretion in the proximal tubules via OATs and OCTs

Question 17

how are organic anions transported into the proximal tubule

Answer 17

organic anion enters via OATs in exchange for aKG

Question 18

what charge to organic anions have and name some drugs that fall into this category

Answer 18

negative - loop and thiazides

Question 19

how are organic cations transported to the filtrate (3)

Answer 19

enters the basolateral membrane via diffusion through an OCT then is exchanged via the apical membrane for Na and through MRD1 protein

Question 20

what charge to organic cations have and name some drugs that fall into this category

Answer 20

positive - potassium sparin diuretics