Pharmacology 3: Other Renal Drugs

Question 1

how do osmotic diuretics enter the nephron

Answer 1

given IV - by glomerular filtration and are not reabsorbed

Question 2

how do osmotic diuretics work (2)

Answer 2

1) increase osmolarity of filtrate which attracts water and sodium across 2) opposes water reabsorption in some parts of the nephron

Question 3

where do osmotic diuretics act in the nephron

Answer 3

proximal tubule

Question 4

what are clinical indications for osmotic diuretics (2)

Answer 4

1) prevents acute hypovolaemic renal failure by maintaining flow 2) urgent treatment of raised ICP or raised intraoccular pressure (increases plasma osmolarity)

Question 5

what are adverse effects of osmotic diuretics (2)

Answer 5

transient expansion of blood volume, hyponatramia

Question 6

how can hyperglycaemia cause osmotic diuresis

Answer 6

reabsorptive capacity in proximal tubule by SGLT1/2 is exceeded - glucose stays in filtrate and causes water to be excreted with it

Question 7

how can iodine radiocontrast dyes cause osmotic diuresis

Answer 7

dye is filtered but not reabsorbed which increases osmolarity of the filtrate and causes fluid to be excreted

Question 8

name an osmotic diuretic

Answer 8

IV mannitol

Question 9

how do carbonic anhydrase inhibitors work

Answer 9

carbonic anhydrase supplies H for Na/H exchange so this is inhibited - also excreted HCO3 with some Na, K and H20

Question 10

what can carbonic anhydrase inhibitors cause

Answer 10

metabolic acidosis and alkaline diuresis

Question 11

when are carbonic anhydrase inhibitors used

Answer 11

glaucoma after surgery, prophylaxis of altitude sickness, infant epilepsy

Question 12

what other agents can alkalise urine and why is this useful

Answer 12

citrate salts - relieves dysuria, prevents weak acid crystals, enhances excretion of weak acids

Question 13

where is aldosterone released from and what does it eventually cause

Answer 13

adrenal cortex –> enhanced tubular Na reabsorption and retention

Question 14

how does aldosterone effect Na/KATPase and ENaC to increase Na reabsorption

Answer 14

increases synthesis of Na/KATPase pump (K excretion) /// increases activity of ENaC which is a Na channel

Question 15

where is vasopressin released from and what does it eventually cause

Answer 15

enhanced H2O reabsorption by increases number of aquaporin channels in apical membrane

Question 16

what is neurogenic diabetes insipidus

Answer 16

lack of ADH (vasopressin) released from post pit which causes increases water excretion

Question 17

how is neurogenic diabetes insipidus treated

Answer 17

desmopressin

Question 18

what effects do nicotine and ethanol have on ADH

Answer 18

ethanol inhibits ADH secretion and nicotine enhances ADH secretion (raised BP)

Question 19

what is nephrogenic diabetes insipidus and what usually causes it.

Answer 19

nephron does not respond to vasopressin - usually caused by X-linked recessive gene on V2 receptor

Question 20

how do you treat nephrogenic diabetes insipidus

Answer 20

no current treatment

Question 21

what drugs can cause vasopressin inhibition in the kidneys (3)

Answer 21

lithium, demeclyocyline (AB), vaptans

Question 22

when is vasopressin used in children

Answer 22

bedwetting (nocturnal enuresis) >10

Question 23

how do vaptans/ aquaretics work

Answer 23

competitive antagonist of vasopressin receptor (v1 and 2) - stops aquaporins being activated and causes water excretion with no Na loss

Question 24

what can vaptans cause

Answer 24

hypernaetraemia

Question 25

what are clinical indications for vaptans

Answer 25

HF, hypervolaemic hyponatremia, SIADH

Question 26

what is the vaptan used in SIADH

Answer 26

tolvaptan

Question 27

how is glucose reabsorped in the nephron and where

Answer 27

in the proximal tubule by SGLT1/2 (some secondary active transport and facillitated diffusion)

Question 28

where is SGLT1 also located

Answer 28

intestines

Question 29

what is the renal threshold for glucose and what can happen when this is exceeded

Answer 29

11mmol - glucosuria

Question 30

what effect on glucose do SGLT2 inhibitors cause

Answer 30

excretion of glucose, decreased HbA1c, weight loss (through calorie loss)

Question 31

name 3 SLGT2i

Answer 31

canagliflozin, dapagliflozin, empagliflozin

Question 32

how are prostaglandins formed

Answer 32

formed from fatty acid and arachidonic acid by COX 1 and 2

Question 33

what are the 2 main prostaglandins produced by the kidneys

Answer 33

PGE2 (formed by medulla), PGI2 (formed by glomeruli)

Question 34

what are the actions of the kidney prostoglands and what causes them to be formed

Answer 34

synthesised in response to: ischaemia, trauma, angiotensin II, ADH and bradykinin (low BP and vasoconstriction) // cause vasodilation and sodium excretion

Question 35

what effect on GFR can prostaglandins have

Answer 35

increase GFR by vasodilation of afferent arterioles and release of renin from granular cells (RAAS)

Question 36

how do you inhibit the formation of prostaglandins and which drugs can do this

Answer 36

inhibit COX enzyme - NSAIDs

Question 37

what 3 drugs are said to cause the ‘triple whammy’ effect on the kidneys

Answer 37

ACEi/ diuretics and NSAIDs

Question 38

how is uric acid formed

Answer 38

catabolism of purines

Question 39

what foods are purines typically found in

Answer 39

red meat

Question 40

how does elevated urate predispose gout

Answer 40

crystals are deposited in joints and soft tissue

Question 41

name 2 drugs uses to treat gout and how they work

Answer 41

uricosuric agents (probenecid and sulfinpyrazone) - block reabsorption of urate in proximal tubule

Question 42

name a drug that inhibits urate synthesis and it’s drug class

Answer 42

allopurinol - xanthase oxidase inhibitor